1995 Bay Science Conference Abstracts

Item Type book

Publisher National Oceanographic and Atmospheric Administration, Atlantic Oceanographic and Meteorlogical Laboratory

Download date 28/09/2021 19:27:13

Link to Item http://hdl.handle.net/1834/18190 95ab

Algal Blooms & Zooplankton

1995 Abstracts

● Blue-Green Algal Blooms in - Edward J. Phlips ● Microalgae of Florida Bay - Karen A. Steidinger ● Phytoplankton Dynamics Studies in Florida Bay - Carmelo R. Tomas ● Spatial and Temporal Patterns of Phytoplankton Bloom in Florida Bay as Measured by Taxonomically Significant Algal Accessory Pigments - Laurie L. Richardson ● Zooplankton Grazing and Production in Florida Bay - G.S. Kleppel ● Zooplankton in Florida Bay - Peter B. Ortner

Circulation Models & Tides

1995 Abstracts

● Analysis of TOPEX/Poseidon Satellite Altimeter Data for Determining Sea Surface Height Variability as Boundary Conditions for Nested Florida Bay Numerical Models - George A. Maul ● Automated In Situ Monitoring of Meteorological and Oceanographic Parameters on

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the Florida Keys Coral Reef Tract and in Florida Bay - S.L. Vargo ● Florida Bay Circulation - Ned P. Smith ● Florida Bay Circulation and Exchange Study - Thomas N. Lee ● Hydrodynamic Modeling of Florida Bay - Boris Galperin ● A Mass-Balance Model of Salinity in Florida Bay: A Tool for Research and Management - W.K. Nuttle ● A Preliminary Modeling Study of Circulation and transport in Florida Bay - Y. Peter Sheng ● Review and Evaluation of Selected Features of the Natural Systems Model, South Florida - Jerad D. Bales ● Salinity and Current Patterns in Western Florida Bay - John D. Wang ● A Study to Define Model and Data Needs for Florida - John D. Wang

Contaminants & Toxins

1995 Abstracts

● An Ecotoxicological Assessment of Pesticide and Urban Nonpoint Source Runoff into Florida Bay and Surrounding Environments - Geoffrey I. Scott ● Monitoring Changes in the Estuaries of the United States: The Environmental Monitoring and Assessment Program in Florida Bay - Kevin Summers ● Oyster and Sediment Contaminant Levels and Trends in South Florida - A. Y. Cantillo

Fisheries

1995 Abstracts

● Age, Growth, Mortality, Fecundity, and RNA-DNA Analysis of Spotted Sea Trout, Cynoscion Nebulosus, in Florida Bay - Dana M. Elledge ● Assessment of Trophic Structure, Mercury Levels, and Responses of Fish and Shellfish to Changes in Habitat in Florida Bay -Donald E. Hoss ● The Effects of Hydrology on Fish Species of the Florida Bay Mangroves Zone: Preliminary Results - Jerry Lorenz

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● Fish and Shrimp Population on Seagrasses-Covered Mud Banks in Florida Bay: 1984-86 Versus 1994-95 - R.E. Matheson, Jr. ● Marine Fisheries-Independent Monitoring Program - James A. Colvocoresses ● Status of Gamefish Harvest Monitoring in Florida Bay, National Park - Thomas W. Schmidt

Hydrology

1995 Abstracts

● Baseline Information on the Quality of Nearshore Waters of The Florida Keys: Identifying Trends and Variability - William Miller ● A Comparison of Mercury in Estuarine Fish: Lagoon and Florida Bay- Douglas G. Strom ● A Comprehensive Groundwater Modeling System for Evaluating the Impacts of the C-111 Canal on Regional Water Resources - David R. Richards ● Dynamics of Groundwater, Surface Water and Salinity Related to the Mangrove/ Marsh Ecotone - William K. Nuttle ● Freshwater Flows into East Florida Bay - Eduardo Patino ● Geophysical Mapping of Fresh/Saltwater Interface - David V. Fitterman ● Hydrodynamic Modeling for Evaluation of the Impacts of the C-111 Canal on Regional Water Resources - Lisa C. Roig ● Hydrogeologic Aspects of Sewage Disposal in the Florida Keys - E.A. Shinn ● The Importance of Taylor Slough Hydrology on Salinities in Florida Bay - Robert A. Johnson ● Monitoring and Evaluation of Radar Measured Rainfall Estimates Over Florida Bay and the Everglades - Paul T. Willis ● Reconstruction and Simulation of Episodic Meteorological Events and Local Weather Regimes Which Affect the South Florida Ecosystem - Craig Mattocks ● Submarine Groundwater Discharge - Jeffrey Chanton ● Visual Mapping of Water Quality in Florida Bay and Adjacent Waters - Bill Sargent

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Mangrove Ecology

Abstracts 1995

● Mangrove Mortality in Florida Bay - P. Carlson ● Patterns of Vegetation and Mangrove Die-Back on Florida Bay Keys - Thomas V. Armentano

Marine Endangered Species

Abstracts 1995

● Breeding Populations of Bald Eagles and Ospreys in Florida Bay - William B. Robertson, Jr. ● Research, Monitoring and Modeling of the Endangered American Crocodile (Crocodylus acutus) in Florida Bay - Frank J. Mazzotti ● Spatial Analysis of Florida Bay - Joan A. Browder ● Studies of Marine Turtles in Florida Bay - Barbara A. Schroeder

Mollusks & Crustaceans

Abstracts 1995

● The Effect of Changing Juvenile Habitat on Spiny Lobster Recruitment - William F. Hernkind ● Mapping Florida Bay Benthic Assemblages: Using Mollusks to Assess Faunal Change - William G. Lyons ● Pink Shrimp as Indicators of Habitat Health in Florida Bay - Joan Browder ● Sponge Biomass Estimates in the Upper and Middle Keys, with Reference to the Impact of Extensive Sponge Mortalities - John M. Stevely

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● Temporal and Spatial Variation in Seagrass Associated Fish and Invertebrates in Western Florida Bay: A Decadal Comparison - Michael B. Robblee

Salinity & Nutrients

Abstracts 1995

● The Florida Bay Watch Volunteer Program - Fran Decker ● Marine Physical Monitoring in - DeWitt Smith ● Nutrient Exchange Between Florida Bay and the Everglades' Salinity Transition Zone - Enrique Reyes ● Nutrient Exchange Between Florida Bay and the Everglades' Salinity Transition Zone: The Importance of Transformations in Mangrove Wetlands - Daniel L. Childers ● Nutrients Dynamics and Limitation in Florida Bay - Wayne S. Gardner ● An Overview of SFWMD Research in the Florida Bay - Everglades Ecotone - D.T. Rudnick ● Sediments, Episodic Land Runoff, and Localized Episodic Groundwater Flushing as Nutrient Sources to South Florida Coastal Waters - Larry E. Brand ● A Study of the Organic Carbon Flux in Florida Bay - Peter K. Swart ● Water Quality Monitoring in Florida Bay: Insights into the Biogeochemistry of the Subtropical Bays and Estuaries of Southwest Florida - James W. Fourqurean

Seagrass Ecology

Abstracts 1995

● Benthic Macrophyte and Invertebrate Distribution and Seasonality in the Florida Bay - Everglades Ecotone: Influence of Salinity Variation - Douglas Morrison ● Benthic Macrophyte Seasonal and Longer-Term Patterns in Florida Bay Along the Key Largo Shoreline - Douglas Morrison ● Florida Department of Environmental Protection Fisheries Habitat Assessment Program (FHAP): An Assessment of Macrophyte Distribution and Abundance on a

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Florida Bay-Wide Scale - Michael J. Durako ● Habitat Inventory and Change in Seagrass and Other Aquatic Beds - Frank J. Sargent ● The Influence of Salinity Fluctuation on Submersed Vegetation at the Land Margin of Northern Florida Bay - Clay L. Montague ● Long-Term Seagrass Monitoring Stations on Cross Bank: the Effects of Long-Term Manipulation of Nutrient Supply on Competition Between the Seagrasses Thalassia Testudinium and Halodule Wrightii in Florida Bay - James W. Fourqurean ● Primary Productivity and Standing Stock Estimates of Benthic, Epiphytic, Plankton, and Seagrass Communities of Florida Bay - Paul V. Zimba ● Resource Health Issues in Florida Bay: Linking Disease and Mortalities - Jan H. Landsberg ● Seagrass Cover-Abundance and Distribution in Northeast Florida Bay Downstream From the C-111 Canal and Taylor Slough - Lee Hefty ● Spatial and Temporal Variations in Seagrass Biomass and Productivity Across Florida Bay - Jay C. Zieman

Sedimentation & Paleoecology

Abstracts 1995

● An Approach to the Retrospective Analyses of Salinity in Florida Bay Using Carbon and Oxygen Isotopes from Mollusk Shells - Robert B. Halley ● Documenting the Styles of Sedimentation and Contained Historical Sedimentary Record in Shallow Marine Environments in and Adjacent to Florida Bay, South Florida - H.R. Wanless ● Florida Bay Ecosystem: Measuring Historical Change - G. Lynn Brewster-Wingard ● Florida Bay Salinity: Fragile Links Between Sediments, Sea Level, and Onshore Water Management - Robert B. Halley ● A History of Salinity and Eutrophication in Florida Bay Using Stable Oxygen and Carbon Isotopes from Scleractinian Corals - Peter K. Swart ● The Hydrology and Geochemistry of Mangrove Mud-Islands in Florida Bay - Phillip A. Kramer

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● Natural and Anthropogenic Events Impacting Florida Bay, 1910 - 1994 Time Line - A. Y. Cantillo ● Paleoecology of the Everglades National Park - M.G. Winkler ● Remote Sensing of Water Turbidity and Sedimentation in Florida Bay - Richard P. Stumpf

Return to the Florida Bay Page

Last updated: 06/14/98 by: Monika Gurnée [email protected]

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Algal Blooms & Zooplankton

1995 Abstracts

Zooplankton Grazing and Production in Florida Bay

G.S. Kleppel, Oceanographic Center, Nova Southeastern University, Dania, FL 33004; Carmelo Tomas, Florida Marine Research Institute, Department of Environmental Protection, St. Petersburg, FL; C.A. Burkart, E. Kerby, and L. Houchin, Oceanographic Center, Nova Southeastern University.

Studies of zooplankton feeding and production are underway in Florida Bay as part of an ongoing investigation of plankton dynamics by FMRI and its academic collaborators. The zooplankton component of the program involves measurement of phytoplankton pigments (chlorophylls and carotenoids), copepod and microzooplankton grazing rates and copepod egg production rates and egg viability in the Gulf, transitional and interior regions of the bay. The conceptual basis of the program is that changes in dissolved nutrients and hydrodynamics have shifted the distribution of primary production in the bay from the benthos (i.e. seagrass) to the water column (phytoplankton). The emphasis of the project is on phytoplankton dynamics and, particularly, on those conditions that result in blooms. Two hypotheses are being addressed as part of the zooplankton component: H1 -- phytoplankton blooms result from high rates of primary production, which exceed the ability of the zooplankton to graze off the biomass, and which, under the appropriate hydrodynamic conditions, result in the accumulation of this excess biomass; H2 -- certain phytoplankton species are not grazed or, when ingested, do not support the zooplankton production necessary to remove excess primary production. It is expected that both sets of processes will be operative at various times.

Measurements are being made on samples from six stations along two southwest to northeast lines (3 stations per line). These extend from approximately the -Florida Bay interface to the inner bay, with stations located in the major basins. The northern line of stations (west to east) includes Sandy, Johnson and Rankin Basins. The southern line consists of Sprigger, Twin and Captain Basins. The first measurements for the zooplankton component of the program were made in June 1995; the study is scheduled to continue until November 1995.

Water samples for hplc-based phytoplankton pigment analysis are collected at each station, each month. The pigment compositions of the six basins are being compared to aircraft observations of bay water color to ascertain whether or not certain phytoplankton community compositions can be discerned from remotely sensed water color attributes.

In addition, each month, microzooplankton grazing rates are measured by the dilution method at Rankin and Captain Basins, and the egg production rates of the dominant copepod species are determined by the

http://www.aoml.noaa.gov/flbay/algal95.html (1 of 14)9/10/2007 2:32:33 PM Algal Blooms & Zooplankton-1995 standard 24-h bottle incubation technique at Rankin, Captain, Sprigger and Sandy Basins. In four of the six monthly study periods the diets and ingestion rates of the dominant copepods are being determined, also by bottle incubations.

Results from the initial (June-July) experiments indicate a close coupling between taxon-specific phytoplankton biomass and copepod (Acartia tonsa) feeding and production. Energy flow is multivorous, incorporating both microbial [nanoplankton --> microzooplankton (ciliate) --> mesozooplankton (copepod)], and classical, herbivorus (netplankton --> mesozooplankton) pathways. Highest production seems to occur when copepod diets are composed of a combination of of phytoplankton (diatoms and dinoflagellates) and ciliates. Viability of Acartia tonsa eggs has been consistently high (>80%) during the summer and seems independent of the egg production rate, which is temporally and spatially variable. Thus, egg production may be a useful correlate to copepod secondary production (P/B). Rankin basin typifies most clearly the transformation from benthic to water column dominated trophic dynamics with high phytoplankton biomass, but also a productive zooplankton fauna.

Zooplankton in Florida Bay: A Project Description

Peter B. Ortner and Michael J. Dagg

The zooplankton of Florida Bay have received comparatively little attention; to date there is not a single published report quantitatively characterizing the resident population nor estimating their contribution to secondary production. One reason for this is that until recently the Bay was extremely clear and seagrasses (and their epiphytes) purportedly dominated primary production. To some this suggested that macroinvertebrates (and teleosts) grazing directly upon macrophytic plant production were the dominant trophic pathway between primary and secondary production. However, the Bay has historically supported substantial populations of teleost larvae (e.g., spotted sea trout), whose primary food (when they are small) are crustacean nauplii. Adjacent shallow water environments like support large populations of estuarine copepods like Acartia tonsa that supplement their phytoplankton diet with macrophytic plant detritus (Roman et al., 1983). Moreover, many macroinvertebrates (e.g. mollusks) have meroplanktonic stages that can be important food resources to larval fish. Last demersal zooplankton like amphipods or harpacticoids can be extremely abundant in shallow water marine systems. In short, zooplankton likely played a significant role in the Bay even when it was clear and phytoplankton blooms were rare. Given the decline in seagrass coverage and the increase in the areal extent and duration of phytoplankton blooms, the role of zooplankton both as consumers of phytoplankton and/or detritus and as food for ichthyoplankton may be changing.

An investigation was launched in the summer of 1994 to answer the following questions:

1) What is the importance of zooplankton consumption in Florida Bay and how does this vary within the Bay as the salinity and temperature distributions change throughout the seasonal cycle?

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2) What is the relative abundance of micro-zooplankton and macrozoplankton and how does this vary within the Bay as the salinity and temperature distributions change throughout the seasonal cycle?

3) What species and types of zooplankton and/or microzooplankton are the primary food of larval and near juvenile fishes? a) What is the distribution and abundance of the prey of larval fish within the Bay and how does this vary within the Bay as the salinity and temperature distributions change throughout the seasonal cycle?

To date bi-monthly samples have been collected over one annual cycle (September 1994 to September 1995) at eight stations in conjunction with Florida DEP juvenile fish sampling. We jointly sample stations at Murray Key, Whipray Basin, Eagle Key Basin, Twin Key Basin, Johnson Key Basin, Duck Key and the south end of the Shell Key Channel. At each we obtained 64um zooplankton net tows as well as 20um deck filtered microzooplankton bucket samples. For the first four bimonthly samples we obtained replicate 150um samples as well at each location. In addition one Night-Day comparison series of twelve 150um net tows was made at Twin Key basin in the South Central region. All samples obtained to date have been enumerated. The effort has been expanded somewhat and now incorporates the following elements:

There are four basic elements in the present research effort.

1) We are continuing our sampling in conjunction with the Florida DEP project (Florida Marine Fisheries Independent Monitoring Program) at the same eight sites on a bimonthly basis. Bimonthly sampling includes 64um mesh net tows for macrozooplankton, 20um sieved bucket samples for nauplii, whole water samples for protozoan microzooplankton.

2) Day/Night intercomparisons will be repeated at Twin Key Basin later in the Fall. Not only abundance will be determined but also gut pigment analysis will be performed to evaluate the consumption of chlorophyll derivative - containing plant materials.

3) Gut contents analyses are being made upon larvae sorted from 150um mesh net tows and upon small- mouthed juveniles and adults sorted from Fla DEP trawl samples taken at the same stations and seine net samples taken nearby.

4) Whether small copepod nauplii in fish guts are predominantly Acartia tonsa will be determined using a species-specific genetic probe. Using Acartia tonsa collected in Biscayne Bay a graduate student of own of us (Ortner) amplified a partial region of the large subunit of ribosomal DNA using the PCR (polymerase chain reaction) method. She then sequenced this region on a LiCor automated sequencer and isolated a unique species-specific area of the subunit. A non-isotopic DNA probe was then prepared for that oligonucleotide sequence signature. The efficiency and utility of this probje is being currently tested using a three primer competitive PCR detection technique. The approach is not only qualitative but potentially quantifiable.

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While this limited effort suffices for initial system characterization and could be continued as restoration (and water flow modification) it is missing an important component. It should be expanded in scope to accommodate microzooplankton grazing activity. In studies we previously conducted in the shallow waters of the northern Gulf of Mexico, microzooplankton grazing has typically equalled or exceeded mesozooplankton grazing and this is characteristic of other subtropical coastal lagoonal environments.

Blue-Green Algal Blooms in Florida Bay

Edward J. Phlips, Susan Badylak, Tammy Lynch, and Phyllis Hansen, Department of Fisheries and Aquatic Sciences, University of Florida/IFAS, Gainesville, Florida 32653.

Florida Bay and the surrounding reefs of the Florida Keys are among the nation's most productive and biologically diverse coastal environments. As the only tropical marine habitat in the continental United States this region is a focal point for sportfishing, diving and tourism, bringing over two billion dollars to the economy of Florida. Recent proliferation of blue-green algal blooms in the bay have raised serious concerns among both commercial and environmental interests about the ecological stability of the bay. Blue-green algal blooms have been implicated in fish kills, sponge die-offs, reductions in seagrass communities and potential alteration of the food webs. State and federal agencies have proposed a major effort to increase freshwater flow to Florida Bay as a means of mitigating these adverse effects, and restoring the character of this vital ecosystem. The potential efficacy of this management strategy must, however, be judged in the context of a clear understanding of the factors which control blue-green algal blooms and the consequences of blue-green algal dominance on the bays ecology.

In August of 1993 we began a Sea Grant funded study to characterize spatial and temporal patterns in the relative dominance of blue-green algae within the planktonic algal assemblage in Florida Bay. In the summer of 1995 this study was expanded with additional Sea Grant funding including, 1) Characterization of spatial and temporal patterns of nutrient and light limitation for planktonic primary production, 2) Determination of the role of salinity in defining the growth and composition of phytoplankton, 3) Determination of the grazing efficiency of zooplankton assemblages on blue-green algal dominated phytoplankton populations, and 4) Characterization of the consequences of blue-green algal dominance for the structure of the food web. This report focuses on the results of the initial phase of this research effort dealing with spatial and temporal variation in the composition and abundance of phytoplankton.

Seventeen sites within Florida Bay (Figure 1) were sampled monthly. The composition and abundance of phytoplankton were characterized using light microscopy of Lugol's preserved samples (Utermohl method) and fluorescence microscopy of live samples. Biovolume estimates were based on the closest geometric shape method. Sub-samples of water were also analyzed for chlorophyll a, TP, TN, Si, suspended solids and color. On-site determinations were made of salinity, temperature, O2, pH, and light

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The spatial and temporal differences observed in phytoplankton standing crops and composition supported the hypothesis that the bay is composed of at least four ecologically distinct regions (Figure 2). The highest standing crops of planktonic algae and cyanobacteria were generally found in the north- central region of the bay, where the small unicellular cyanobacterium Synechococcus dominated the planktonic assemblage. Chlorophyll a concentrations ranged up to 40 mg m-3 in this region, and Synechococcus was responsible for over 90% of total phytoplankton biovolume in most of the samples analyzed. In other regions of the Bay total chlorophyll a concentrations were generally lower and the relative importance of diatoms and dinoflagellates increased in relationship to total phytoplankton biovolume. The north-eastern region of the bay exhibited the lowest standing crops, i.e. chlorophyll a concentrations consistently less than 2 mg m-3. In the south-central region phytoplankton standing crops were low accept in the late fall and early winter when elevated levels of Synechococcus were observed and chlorophyll a values reached 20 mg m-3. Gradients of phytoplankton abundance and composition indicate that these elevated standing crops may result more from the influx of water from the north- central region than in-situ production. In the western region of the bay phytoplankton standing crops were variable but averaged around 5 mg m-3 and the phytoplankton community was typically dominated by diatoms. The significant variability of chlorophyll a concentration and taxonomic composition in the western region may be a consequence of temporal variation in the character and amount of intruding Gulf waters.

The consistently high planktonic chlorophyll a concentrations observed in the central- interior region of Florida Bay may be related to spatial patterns of water circulation and inflow. The impact of tidal water exchange in this region of the bay is reduced by the shallow mudbanks around its periphery (Figure 1). Turnover rates for water and nutrients are, therefore, low compared to the western side of the bay. It is also a region of the bay impacted by inflows of water from the mainland through Taylor Slough (Figure 1). It may be hypothesized that the combined effects of periodic inputs of nutrients from the mainland, nitrogen fixation and low turnover rates heighten the potential for elevated chlorophyll a levels. At the beginning of the second year of the study period, fall '94, extended periods of high rainfall resulted in high levels of freshwater input to the north-central region. Salinities were observed to drop from over 40 ppt to less than 20 ppt and phytoplankton standing crops also declined temporarily. These observations point to a significant role for freshwater inflow in the dynamics of phytoplankton populations.

Phytoplankton standing crops may be further accentuated by the shallow polymictic character of the bay which increases the potential for nutrient recycling through sediment resuspension, i.e. internal nutrient loading. The relatively deep layer of muddy surface sediments in the north-central region present the potential for significant sediment resuspension. The role of internal nutrient loading in the maintenance of high phytoplankton standing crops is well established for in a number of freshwater and marine environments.

References

http://www.aoml.noaa.gov/flbay/algal95.html (5 of 14)9/10/2007 2:32:33 PM Algal Blooms & Zooplankton-1995 Phlips, E. J. and S. Badylak. 1996. Spatial Variability in phytoplankton standing crop and composition in a shallow inner-shelf lagoon, Florida Bay, Florida, USA. Bulletin of Marine Science 58(1).

Phlips, E. J., T. C. Lynch and S. Badylak. 1995. Chlorophyll a, tripton, color and light availability in a shallow tropical inner-shelf lagoon, Florida Bay, USA. Marine Ecology Progress Series. In Press.

Spatial and Temporal Patterns of Phytoplankton Blooms in Florida Bay as Measured by Taxonomically Significant Algal Accessory Pigments

Laurie L. Richardson, Department of Biological Sciences and Drinking Water Research Center, Florida International University, Miami, Florida 33199 .

Background

A quantitative study of phytoplankton bloom dynamics in Florida Bay was initiated in 1994, and is currently funded through August 1997. This research effort was originally part of a project supported by the National Aeronautics and Space Administration (P.I. L.L. Richardson) to determine the use of remote sensing to detect algal accessory pigments and estimate water quality. Field research includes an investigation into the biology of the system, and we routinely collect surface water samples for HPLC analysis of algal pigments (accessory pigments, chlorophyll a, and chlorophyll a degradation products) of different areas of the phytoplankton bloom, as well as measurements of optical properties (surface reflectance), salinity, and temperature. Florida Bay was chosen as a research site due to the optically dense nature of the phytoplankton bloom and the fact that the bloom is not uniform in terms of algal population composition thus is a good field site for discriminating between different algal populations.

An outcome of this project has been documentation of phytoplankton bloom composition, spatial and temporal bloom dynamics, and analysis of the bloom over time and space in terms of correlation with salinity, nutrients (data from Ron Jones), temperature, and dissolved oxygen.

Objectives

The principal objective of the biological component of this research effort is to document the nature of the phytoplankton bloom in terms of population composition, spatial distribution, seasonal variability, and correlation with water quality. The overall goal of this research (not reported here) is to demonstrate the use of hyperspectral remote sensing to detect algal accessory pigments for the study of phytoplankton dynamics.

Methods

http://www.aoml.noaa.gov/flbay/algal95.html (6 of 14)9/10/2007 2:32:33 PM Algal Blooms & Zooplankton-1995 I. Approach. Nine diagnostic algal pigments are quantitatively measured, whose presence indicates overall phytoplankton biomass (healthy and dead) as well as information about specific algal groups. The pigments measured are: chlorophylls, a, b, c; chlorophyllide a; fucoxanthin; diadinoxanthin; zeaxanthin; lutein; B-carotene; and myxoxanthopyll. The presence of these pigments are interpreted as follows: The distribution of chlorophyll a (present in all algae) reflects the overall distribution (and biomass present) of healthy phytoplankton. Chlorophyllide a, a natural degradation product of chlorophyll a, indicates the presence of dead phytoplankton material. Chlorophyll b is present only in Green algae (Chlorophytes) and Prochlorophytes (not phytoplankton). Chlorophyll c1/c2 (a mixture of two types of chlorophyll c which elute together on the HPLC column) indicates the presence of diatoms and dinoflagellates, with fucoxanthin generally indicating diatoms and diadinoxanthin indicating dinoflagellates. Myxoxanthophyll is found only in Cyanophytes (blue-green algae). Lutein, although specific to Chlorophytes (and Rhodophytes, not planktonic), co-elutes with zeaxanthin which is found in many types of algae as is ß-carotene. Thus zeaxanthin and ß-carotene can be used to indicate overall algal abundance, similar to chlorophyll a.

Pigment sampling and analysis are conducted as follows: Florida Bay water samples (2 liters) are collected and filtered onto 4.25 cm GF/F filters, and stored frozen at -70° C. Prior to analysis the samples are thawed and extracted according to the methods of Wright and Shearer (1984). Extracted samples are evaporated (to decrease volume) using nitrogen gas, and the final extract volume is measured to quantify results. 20 µl of a final solution are analyzed using High Performance Liquid Chromatography (HPLC) by injecting onto a Hewlett Packard 1090 HPLC with a 200 x 2.1 mm column containing 5 µm hypersil ODS to separate and identify pigments. An elution gradient similar to that of Mantoura and Llewelyn (1983) is used. Pigments are quantified and identified by an analytical software package incorporated into the system. Samples are run against purified standards of each pigment except myxoxanthophyll, which is quantified by using the standard curve for diadinoxanthin but ratioing the extinction coefficients of myxoxanthophyll and diadinoxanthin. Salinity is measured using a refractometer. [Nutrients were sampled and anlyzed by Ron Jones lab (FIU).]

II. Sampling locations and frequency. Sampling is conducted once per month. Locations vary depending on where the phytoplankton bloom is located during each sampling period. Our routine sites are basins near Rankin, Rabbit, Whipray, and Calusa keys. We also sample, depending on bloom development, at additional sites which include basins near Crocodile, Garfield, Jimmy, Johnson, Manatee, Murray, Old Dan Bank, Peterson, Pollock, Porpoise, and Twin Keys. Several of our sites correspond to sites routinely sampled by FIU's SERP monitoring program. Additional sites are sampled which exhibit the most dense phytoplankton blooms.

III. Project duration. Preliminary investigations began in 1993, and a satisfactory quantitative methodology was adopted in 1994. Quantitative data have been acquired since May, 1994 and will continue through August 1997.

Summary of results to date

http://www.aoml.noaa.gov/flbay/algal95.html (7 of 14)9/10/2007 2:32:33 PM Algal Blooms & Zooplankton-1995 At any given time, the phytoplankton bloom consists of different, patchy sub-blooms in different basins of Florida Bay which exhibit different algal communities. The dominant phytoplankton include cyanobacteria (blue-green algae), diatoms, and dinoflagellates. In addition to this spatial variability, specific sites demonstrate monthly variability. An example of the data set (in this case temporal) is shown in the following table, which presents data (pigments concentrations in µg/l) from Whipray Basin. These data show that the bloom was most pronounced in January, but was healthiest (no chlorophyllide a) in November and December. Changes in the relative amounts of cyanobacteria (myxoxanthophyll) vs. diatoms and dinoflagellates (chl c1/c2) is also evident.

Date Chl a Chlorophyllide a Chl c1/c2 myxoxanthophyll

5/4/94 3.74 0.21 0.16 0.34

6/8/94 3.37 0.13 0.00 0.30

7/7/94 4.41 0.37 0.40 0.38

8/3/94 3.24 0.14 0.19 0.28

10/5/94 5.32 0.00 0.26 0.21

11/2/94 5.07 0.00 0.49 0.48

12/1/94 5.39 0.00 0.60 0.38

1/5/95 10.11 0.85 1.73 0.93

3/22/95 1.07 0.12 0.14 0.13

Each pigment within the data set was also linearly regressed against water quality data acquired at the same time. We found no strong correlation between pigment distribution and variations in salinity, nutrients, or dissolved O2. Salinity, believed by some to be the cause of the Florida Bay bloom, had a correlation coefficient (R2) of 0.003 when regressed against chlorophyll a, and 0.053 against chlorophyllide a. Similarly, pigment regressions against nutrients and dissolved oxygen were non- significant. The only (mildly) significant correlations were found between salinity and temperature (R2 = 0.317). Chlorophyll a and temperature were not significant (R2 = 0.185). The distribution of pigments which occur within the same taxa were, as expected, significantly correlated (for example R2 of fucoxanthin and chlorophyll c = 0.950).

Outlook for remaining work

http://www.aoml.noaa.gov/flbay/algal95.html (8 of 14)9/10/2007 2:32:33 PM Algal Blooms & Zooplankton-1995 This work will continue through August 1997, and is supported by the Ocean Biology program withing NASA's Mission to Planet Earth program. In addition to the data gathering efforts detailed above, the NASA-supported effort consists of determining the feasability of using hyperspectral imaging remote sensing data to study phytoplankton bloom dynamics in Florida Bay. Monthly sampling for determination of accessory pigments, salinity, pH, water temperature and optical measurements will be used to generate a background for analysis of AVIRIS (Advanced Visible-Infrared Imaging Spectrometer) data, acquired by flying this prototype sensor on NASA's ER-2 high altitude aircraft. As the data base increases, perhaps a correlation between algal distribution and water quality will become apparent.

References

Mantoura, R.F.C. and C.A. Llewellyn, "The rapid determination of algal chlorophyll and carotenoid pigments and their breakdown products in natural waters by reverse-phase high performance liquid chromatography", Anal. Chim. Acta, Vol. 151, pp. 297-314, 1983.

Wright, S.W. and J.D. Shearer, "Rapid extraction and high performance liquid chromatography of chlorophylls and carotenoids from marine phytoplankton", J. Chromatog., Vol. 294, pp. 281-295, 1984.

Microalgae of Florida Bay

Karen Steidinger, William Richardson, Earnest Truby, Rachel Bray, Nancy Diersing, and Dave Eaken, Florida Department of Environmental Protection, Florida Marine Research Institute, 100 Eighth Ave. SE, St. Petersburg, FL 33701.

Persistent microalgal blooms have occurred in the western and central portions of Florida Bay since 1991. Blooms of mixed microalgae populations are often dominated by pico- and ultraplankton consisting of blue-greens (cyanobacteria), diatoms, flagellates, and an unidentified sphere. The abundance of these pigmented algae contributes to extensive surface water discoloration, which ranges from yellow-green to brown. Resuspended carbonate sediments and bottom organic material can add to the discoloration and turbidity. Several of the objectives of the Florida Marine Research Institute's Florida Bay Microalgae Study are to 1) determine the planktonic and benthic microalgal species composition, abundance, biomass, and dominant assemblages (biological turbidity), 2) determine the non-biological components of turbidity associated with resuspended inorganic sediments and organic detritus on the same spatial scale, and 3) isolate dominant species into culture for a) laboratory growth limitation experiments and b) exposure studies with filter feeders to determine acceptability of species as food items or the toxicity of species to selected filter feeders. These three objectives address questions B.3 (what limits growth of phytoplankton), B.5 (what is the biological and non-biological cause of turbidity), C.3 (what is the cause of sponge mortality), and D.1 (have altered environmental conditions and habitat affected growth/survival of animals through altered trophic structure and dominance of different microalgae) in the 1994 Science Plan for Florida Bay.

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Six fixed stations, (Sprigger Bank, Sandy Key, Johnson Key Basin, Rankin Basin, Captain Key, and Twin Key) were chosen for monthly water column sampling based on the availability of a historical database or because of their location in relation to past microalgal bloom events. Four of these stations are also sampled for primary productivity and nutrient enrichment bioassays by another group within this Study. Two bloom stations are chosen monthly based on aerial observation of discolored water. Up to 35 additional stations are sampled by The Nature Conservancy's Bay Watch volunteers. Locations for these incidental stations are selected the day before based on aerial overflight observations of discolored water in the western, central, and eastern portions of the Bay. The following variables are measured at the fixed and bloom stations with a Hydrolab Surveyor II or III: salinity, temperature, D.O., pH, and water depth. In addition secchi depth is measured and cloud cover, wind direction, and wind speed are estimated. Four to 20 liters of surface water are collected for laboratory processing and testing for Total Particulate Matter (inorganic and organic seston fractions) following a modification of Strickland and Parsons (1972) and EPA (1990); blue-green algal (cyanobacterial) abundance following a modification of the epiflourescence techniques of Booth (1993) and MacIssac and Stockner (1993); diatom, dinoflagellate, flagellate and other algal group species composition, abundance, and cell volume following the Utermohl method of Lugol's fixed and sedimented samples counted on an inverted microscope and scanning electron microscopy of Lugol's fixed concentrated samples, and single cell isolation of dominant species for establishing clonal cultures in "f/10" or "K/10" media following Guillard and Keller (1984). The incidental stations are treated the same for Total Particulate Matter, blue- green algal abundance but other microalgae are counted by group and not species and abundance is reported numerically rather than by cell volume. In addition, field measurements are salinity by hydrometer, temperature by thermometer, and secchi depth. Monthly sampling started in March 1994 and continues today for the above variables. Data are current for physical-chemical measurements, total particulate matter, and blue-green algal abundance. Results for species composition and abundance at the fixed stations are complete for July 1994 through April 1995 (10 months) and are being calculated for cell volume. Remaining samples are being worked up. Physiological studies (e.g., salinity, temperature, and light) using recently established clonal cultures of the dominant microalgae Synechococcus elongatus, Cyclotella choctawhatcheeana, Chaetoceros wighamii, Rhizosolenia imbricata, and the 2mm picoplankter are being formulated, as are exposure studies with Synechococcus and Cyclotella.

Over 120 diatom, 70 dinoflagellate, and 30 other algal taxa have been identified from Florida Bay during this study; 160 have been identified to species. Scanning electron microscopy and workup of the remaining samples will no doubt increase the identified species to over 250. Of the fixed stations, the two most western stations, Sprigger Bank and Sandy Key, appear to be subject to continual resuspension events as reflected by the presence of organic detritus, benthic diatoms, sponge spicules and inorganic seston (median values of 8.33 mg L-1 and 8.85 mg L-1 respectively). Turbidity is also influenced by blue-greens (103 to 106 per ml), summer blooms of Chaetoceros spp. (6+) and winter blooms of species in the Rhizosoleniaceae (Rhizosolenia imbracata, R. setigera, R. styliformis, Proboscia alata, Pseudosolenia calcar-avis, Dactyliosolen fragilissima, and Guinardia striata). Various combinations of sediment and microalgae can cause the surface waters to appear tan to murky brown. At Sprigger in December 1994, blue-greens dominated numerically and by cell volume. In February 1995, blue-greens

http://www.aoml.noaa.gov/flbay/algal95.html (10 of 14)9/10/2007 2:32:33 PM Algal Blooms & Zooplankton-1995 dominated numercially but diatoms dominated in cell volume. Many of the Rhizosolenia cells were senescent and apparently the product of rapidly dividing populations. In April, blue-greens dominated numerically but diatoms dominated in cell volume. The two north central stations, Johnson and Rankin basins, have some of the highest chlorophyll a values recorded (up to 40 µg L-1). Johnson is more influenced by the Gulf as are the most western stations, e.g., resuspension, summer Chaetoceros and winter Rhizosolenia blooms. Also, this is the station where the picoplankter and small flagellates start to appear in substantial numbers. Rankin literally is the hot spot for the small-sized blue-greens, picoplankters, flagellates, and Cyclotella, and it also has resuspension events as evidence by benthic species and detritus. In December 1994, blue-greens dominated numerically but diatoms and flagellates dominated by cell volume. In April, blue-greens and picoplankters dominated numerically, but diatoms dominated by cell volume. For the most eastern fixed stations, Captain and Twin, dominance can shift between blue-greens, flagellates and picoplankters to diatoms and dinoflagellates. Typically lower chlorophylls were recorded and resuspension events were not common, e.g., median inorganic seston values were 3.13 mg L-1 and 2.16 mg L-1 respectively.

The planktonic and benthic chlorophyll-bearing microalgae of Florida Bay are diverse and range from temperate to tropical species, many are euryhaline, some are stenohaline. Many have been recorded from south Florida waters previously, some are new to the region, and some are just undescribed species. The dinoflagellates Gambierdiscus toxicus, Prorocentrum belizeanum, Pyrodinium bahamense var. bahamense (bioluminescent species) and others identify this Bay as tropical/subtropical. From a microalgal perspective, the Bay is unique in several combined features: it is rich in species, many of which are mucus producers; it has persistent mixed microalgal blooms, often dominated by the smaller size fractions; it has at least 15 known toxic dinoflagellate, diatom, and flagellate species; and it lacks the dominance of two common and abundant estuarine/coastal diatoms, Skeletonema costatum and Asterionellopsis glacialis. As in many Florida bays and other coastal areas, microalgal biomass as chlorophyll a and primary production can exceed the water column biomass and production (Zimba, unpublished).

Phytoplankton Dynamics Studies in Florida Bay

C. R. Tomas, and B. Bendis, Florida Department Environment Protection, Florida Marine Research Institute, St. Petersburg.

The development of extensive phytoplankton blooms in Florida Bay marked a major departure from a previous status where primary production was dominated by benthic macrophytes resulting in a limpid, nutrient poor water column having a low phytoplankton biomass. These pelagic blooms, ushering major changes in biomass distribution also imposed altered trophic dynamics and structure. Among the major questions regarding these blooms are what major species compose the blooms, how are they distributed and how do they change with space and time? Equally important are questions related to the rates of change, growth, and factors stimulating and limiting the blooms. Finally, how do these blooms influence the trophic structure and how is this translated into the presence and loss of species from Florida Bay?

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The first questions relate to the description and quantification of biomass while the latter two relate to dynamic processes regulating the biomass. Studies addressing both types of major questions are included in the FDEP/FMRI phytoplankton program for Florida Bay.

Ongoing studies were begun nearly 2 years ago to define the spatial and temporal changes in phytoplankton species composition, abundance and biomass measured as chlorophyll a in Florida Bay. Additional studies of phytoplankton processes were also initiated 20 months ago. Since March 1994, nutrient bioassay studies have been conducted monthly on natural populations from four fixed stations in the Bay. These studies were prompted from the previously published results of Fourqurean, Jones and Zieman (1993) describing nutrient analyses from the Bay indicating the general paucity of inorganic nitrogen and phosphorus and the conclusion that phosphorus was limiting the blooms in most of the Bay regions. While nutrient ratios are informative, our objectives were to verify independently the type and degree of limitation as demonstrated directly by the phytoplankton components of the Florida Bay ecosystem. Growth stimulated by the nutrient addition, preference for specific nutrients, and inhibition of lacking major nutrients could be used to verify limitation as well as to compliment the biomass data. These observations would be useful in defining the intrinsic growth rates of phytoplankton in the Bay and what specific nutrients were limiting it.

In addition to the nutrient bioassays, estimates of primary production were begun in September 1994 on samples from the same 4 fixed stations where bioassays were being conducted. Using the 14C labelled bicarbonate, measurements at 10 natural light levels for duplicate bottles of samples from each station were made to define daily primary production rates. The production values would be helpful in defining the variation in productivity within Florida Bay, to give data from which comparisons can be made to other coastal regions and to allow a comparison of pelagic and benthic production.

A third component, begun in June 1995, is examining secondary production as measured by zooplankton grazing, copepod egg laying and microzooplankton feeding. This portion of the trophic dynamics studies are presently being conducted under contract to the FMRI phytoplankton group. Primary and secondary production will, at a future date, be coupled with species abundance and composition in defining the influence of blooms on trophic flow. This component will not be discussed here.

To date, over 2000 individual bioassay tests have been conducted on natural phytoplankton populations from the four fixed stations. These stations were chosen to reflect the variability within the bay and monitor major regions. The Captain Key basin station reflects features generally found in the oligotrophic eastern sector of the Bay while samples from Rankin Lake, where maximum phytoplankton biomass persisted, represents the most heavily impacted bloom station. Samples from Sprigger Bank and Sandy Key in the western Bay are areas where waters from the South West Florida shelf and Bay intermix. Eight treatments run in triplicate were tested for each station each month. Two treatments included low and high phosphorus (5, 10 µM/L P), another two low and high levels of nitrogen (15 and 30 µM/L) equally as nitrate and ammonia, two additional treatments with low and high combination additions of nitrogen, phosphorus and constant level of silica. A total addition consisted of N, P, Si, vitamins, and trace metals including chelated iron. A non enriched control completed the eighth treatment. Growth was monitored by in vivo fluorescence using a Turner Design fluorometer and run in

http://www.aoml.noaa.gov/flbay/algal95.html (12 of 14)9/10/2007 2:32:33 PM Algal Blooms & Zooplankton-1995 a constant temperature waterbath having continuous illumination of approximately 50-90 µEm-2s-1 cool white fluorescent light. The assays were run for 3 days then terminated and harvested for final extracted chlorophyll analysis. By the third day, clear responses were detectable and further incubation resulted in declines of high biomass samples. An alternate exclusion assay was also done to confirm the limitation. For these assays, all nutrients were added to sample tubes except one giving -N, -P and -Si treatments. These assays were run in duplicate along with the addition assays.

Captain Key basin is the one station that continuously showed phosphorus limitation. Stimulated by phosphorus or limited by its absence, populations from this station indicated the limited availability of this nutrient to the eastern sector. The biomass of this station was consistently low compared to the other stations. With the exception of a late winter expansion of the blooms this station responded consistently in this manner. Rankin Lake area which often had the highest phytoplankton biomass responded modestly to the nutrient bioassays enrichments indicating a varying limitation between nitrogen and phosphorus. The response at Rankin Lake was as much a function of the heavy biomass nearing the carrying capacity of the system as it was to the exact limiting nutrient(s). During periods when biomass was low at Rankin, bioassays responded in a similar manner to those done at other stations. Both Sprigger and Sandy Key stations gave bioassay results indicating varying limitation of nitrogen, rarely phosphorus but definite stimulation by the addition of silica. This presumably is due to a major diatom component of the phytoplankton population which can dominate most of the year in this area. Other inner stations, particularly Rankin Lake, have a shared dominance particularly between bluegreen algae and diatoms. The emergent nutrient picture for Florida Bay is that the nutrient limitation of phytoplankton reflects the complicated morphometry of the whole basin offering a mosaic of limitation segmenting the isolated eastern basin, heavily impacted mid central basin and shelf influenced western area.

To date, 1,400 individual estimates of primary production were made for the 4 fixed stations in Florida Bay. Primary production measurements from the bay stations varied directly with the biomass and consistently showed high light limitation throughout the year. Light saturated production varied from 0.8 to > 1 g C/m-3/day-1 with highest values occurring in the western bay stations. Primary production at the station having the highest biomass (Rankin Lake) was often exceeded by the western stations particularly when diatoms were abundant at the near shelf stations. Presumably the phytoplankton composition, being dominated by a bluegreen algal component (Synechococcus) at Rankin Lake, had different photosynthetic efficiencies than stations having lower biomass but different species composition.

The lowest production was consistently measured at the Captain Key station which accompanied the low biomass found there. A complete cycle of these studies is yet to be completed and the data is presently being analyzed. Estimates of photosynthetic efficiencies and carbon turnover rates are expected to further define the full range of variability in phytoplankton primary production for Florida Bay.

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Last updated: 04/22/98 by: Monika Gurnée [email protected]

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Circulation Models & Tides

1995 Abstracts

Review and Evaluation of Selected Features of the Natural Systems Model, South Florida

Jerad D. Bales, Eric Swain, L.L. DeLong, U.S. Geological Survey, 3916 Sunset Ridge Road, Raleigh, North Carolina 27607, voice: 919-571-4048 fax: 919-571-4041, email: [email protected].

The Natural Systems Model (NSM) was developed in the late 1980's by the South Florida Water Management District (SFWMD) to simulate the hydrology of South Florida for pre-colonization conditions. The NSM includes none of the hydromodifications that have been made in south Florida since European colonization. In addition, the NSM includes estimated topographic and vegetative conditions as they might have been prior to colonization. Because historic climatic data are not available, recent climatic data are applied to simulate the hydrology of the natural system. using algorithms and data from the South Florida Water Management Model (SFWMM).

The SFWMM, initially developed by the SFWMD in the late 1970's and early 1980's, is a regional scale hydrologic model that simulates the hydrology and the highly-managed water system in an approximately 7,600 mi2 (square mile) area of South Florida. Unsteady ground- and surface-water conditions and canal flows are simulated for time-invariant land-use and water management scenarios. The NSM uses the same climatic input data, and similar model algorithms and computational schemes as the SFWMM. Model parameters from the calibrated SFWMM are transferred directly to the NSM. Results from the NSM can be compared with output from the SFWMM for the same set of climatic inputs to estimate the effects of hydromodifications and water management on the natural hydrology.

The NSM cannot be calibrated and tested using traditional approaches. Accurate, detailed information on historic vegetative and topographic conditions, which is required for NSM operation, is largely unavailable. Hydrologic data from the natural system also are unavailable, so model performance cannot be directly tested. The performance of the NSM primarily has been evaluated by using two approaches. First, because the fundamental algorithms used in the NSM are the same as those in the SFWMM, and because the SFWMM appears to perform adequately, it has been assumed that the NSM is properly simulating the important hydrologic processes. Second, a series of sensitivity tests and uncertainty analyses has been performed on the NSM to identify (1) the sensitivity of model output to changes in selected model parameters and (2) geographic areas in which the simulated hydrology is most sensitive to changes in model parameters.

The NSM has been proposed as the "best available tool" for setting hydropattern targets for use in

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Everglades restoration efforts. Restoration costs may exceed one $1 billion, and water diverted to the Everglades might not be available for a variety of important, competing uses along the southeast coast of Florida, which has a population of almost 4 million. Consequently, decisions made using NSM results could have important and direct implications for the south Florida region.

In July 1995, a study was initiated by the U.S. Geological Survey in cooperation with the Jacksonville District of the U.S. Army Corps of Engineers and with assistance from the South Florida Water Management District. The objective of the study is to determine if the NSM provides a reasonable simulation of South Florida hydrology for pre-colonization conditions, or the natural system, by using recent climatic data. The absence of data from the natural system for model testing requires the application of novel procedures to determine if NSM results are "reasonable." Only selected components and features of the model are to be reviewed because of the limited resources and time available for the review.

Review topics have been formulated as a series of questions addressing hydrologic processes and their numerical representation and calibration issues. In general, topics are being addressed by a combination of (1) development and application of a simplified, but flexible computer code which includes key algorithms of the NSM; (2) application of the new code, NSM, SFWMM, and other appropriate models or analytical solutions for selected conditions, and evaluation of the results; (3) review of scientific literature concerning the formulation of processes simulated by the NSM and (4) documentation of the SFWMM calibration and testing results, and of the findings of experienced NSM users.

Issues related to model representation of hydrologic processes and the numerical approximation of those processes include the following:

• At what spatial and temporal discretization is NSM numerically convergent?

• What is the effect of more refined vegetation information on simulated results?

• What is the effect of spatial variation in rainfall on simulated results?

• How does the delineation of evapotranspiration zones affect model results?

• How are the physical processes of evapotranspiration, channel flow, and ground-water flow represented in NSM?

The specific calibration issues to be addressed are:

• Is the SFWMM calibration unique? If not, what are the implications for the NSM calibration?

• Are there marked differences in the quality of the SFWMM results for low and high flows?

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• What are some possible pseudo-methods for evaluating the performance of the NSM?

• Are there geographic areas for which the model appears to perform better than other areas?

This investigation is to provide an independent, scientific review and documentation of key components of the NSM. Results from the study should provide documentation on strengths, limitations, and appropriate applications of the model. Physical processes and (or) computational aspects of the model which should benefit from enhancement, additional research, or improved data also are to be documented.

Hydrodynamic Modeling of Florida Bay

Boris Galperin, Mark Luther, Meredith Haines, Department of Marine Science, University of South Florida, 140 7th Avenue SouthSt. Petersburg, FL 33701.

Results of modeling circulation and salinity distributions in Florida Bay are discussed. The hydrodynamic model used in this study is an advanced version of the Blumberg - Mellor model in which semi-implicit integration in the horizontal is incorporated. Not only this model affords to increase the computational time step beyond the limit imposed by the CFL condition in the explicit models, but it also accomodates algorithms describing drying and flooding of the coastal areas. These features are very important for Florida Bay because of its shallowness.

The most important diagnostic and prognostic parameters calculated by the model are:

1. Free surface elevation;

2. Horizontal velocity components;

3. Vertical velocity component and its analog in the sigma-coordinate system which is the velocity component normal to sigma-surfaces;

4. Salinity S;

5. Temperature T;

6. Density;

7. Turbulence kinetic energy;

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8. Turbulence macroscale;

9. Vertical eddy viscosity;

10. Vertical eddy diffusivity;

11. Two components of the bottom stress vector;

12. Concentration of a conservative tracer C.

The basic equations are cast in a free surface and bottom following, sigma-coordinate system in the vertical direction. In the horizontal, the model uses an orthogonal, curvilinear coordinate system conforming to the coastline. The vertical mixing processes are calculated using a level 2.5 closure scheme by Mellor and Yamada. The subgridscale representation in the horizontal is provided by the Smagorinsky model in which the nonlinear horizontal eddy viscosity depends on grid resolution and the rate of local mean strain.

The model can be executed in the vertically integrated, barotropic mode and fully three-dimensional, baroclinic mode. Despite the use of a semi-implicit horizontal integration scheme, the model is still maximally optimized to efficiently run in a parallel processor environment.

The curvilinear coordinate grid designed for this study is shown in Fig. 1. It contains 72 grid boxes along the east - west direction and 56 points in the north - south direction. On the western side of the model domain an open boundary extends from to Marathon, where forcing functions are prescribed. On the north-eastern side, the grid borders with . The grid has relatively coarser resolution in its western part adjacent to the west Florida shelf while resolution is increasingly refined towards the north-eastern part where higher gradients are expected due to the topographical constraints, fresh water runoff, etc. The digitized bottom topography for this study was kindly provided by the National Park Service.

Preliminary two- and three-dimensional simulations of circulation in Florida Bay were conducted with the model forced by the tidal elevation along the open boundary using the tidal prediction model. The necessary tidal harmonic constants of 5 tidal constituents, namely M2, S2, N2, K1, and O1 were obtained for Marathon and for the vicinity of Cape Sable (Station M5 of Harbor Branch Oceanographic Institution). Tidal elevations at grids points between the two stations were calculated by linear interpolation. Temporal variations of temperature and salinity data have been prescribed along the open boundary using data at nearest Everglades National Park MMN stations, namely Johnson Key and Peterson Key. Wind data from the nearby Joe Bay station has been collected and used to force the model. Information on freshwater inflows to the Bay was not available so that a constant inflow distributed over 65 grid points along the north-eastern part of the grid has been assigned along the south Florida mainland to determine its impact on the hydrodynamic and salinity regimes of Florida Bay.

http://www.aoml.noaa.gov/flbay/circ95.html (4 of 20)9/10/2007 2:32:34 PM Circulation Models & Tides-1995 Some calibration runs have been made for the period of September 1 to December 31, 1993. Data during this four month period were available for comparison with model results. Generally, simulations in the vertically-integrated mode agreed well with the fully 3D simulation. The best agreement was achieved for free surface elevation. It was found that some parts of Florida Bay are consistently drying and flooding during the tidal cycle; work is being done to better identify and quantify this phenomenon.

At the present time, simulations are being conducted with various values of fresh water runoff, to understand the effect of the runoff on circulation and salinity distributions in Florida Bay. Results of these simulations will be presented at the Florida Bay Science Conference.

Florida Bay Circulation and Exchange Study

Thomas N. Lee, University of Miami/RSMAS, 4600 Rickenbacker Causeway, Miami, Fl 33149; Elizabeth Johns, NOAA/AOML, Miami, Fl 33149.

A new two year observational study of the interaction and exchange of Florida Bay with the connecting coastal waters of the Gulf of Mexico and the Atlantic in the Florida Keys will start­up in early winter 1995 with support from NOAA/COP Florida Bay Program. The research is designed to address several of the key scientific questions presented in the NOAA Florida Bay Implementation Plan as critical to understanding the functioning of the ecosystem and possible future evolution from restoration actions. In particular, the research will address the following questions:

1) To what degree is the circulation of water within Florida Bay coupled to that of the surrounding coastal and oceanic environments?

2) What is the relationship of surface and groundwater flows through the Everglades to the salinity of Florida Bay?

3) Is the quality of the water flowing from the Bay contributing to the degradation of corals along the reef tract of the Florida Keys in the Atlantic Ocean?

Observational methods consist of a combination of synoptic shipboard surveys, in­situ moorings and Lagrangian surface drifters to describe and quantify the circulation within the Bay as related to local forcing and coupling with the waters of the Atlantic and Gulf. These data will be used to determine the rates and pathways of material exchange across the open boundaries to the Bay, which are needed to understand the transport and exchange of planktonic communities with nearby coastal environments, and the recruitment of larvae and young juveniles to the Bay's nursery grounds. These new observations will also provide necessary boundary conditions for future physical and biological models.

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Analysis of Topex/Poseidon Satellite Altimeter Data for Determining Sea Surface Height Variability as Boundary Conditions for Nested Florida Bay Numerical Models

George A. Maul, Division of Marine and Environmental Systems, Florida Institute of Technology, 150 West University Boulevard, Melbourne FL 32901-6988.

Numerical models of Florida Bay circulation require the highest possible spatial resolution in order to determine details of the three-dimensional flow. Accordingly, they are nested within lower spatial resolution local- and/or regional-scale circulation models to provide the boundary conditions associated with ocean forcing external to the Bay area. Dynamic consistency of the lower spatial resolution models must be tested by independent observations; satellite measurements of sea surface height (SSH) variability is investigated herein for that purpose.

Altimetry from TOPEX/Poseidon is considered the best means of estimating SSH variability with the current crop of spacecraft. The altimeter measures the range from the orbiting vehicle to the sea, and precise tracking measures the position of the satellite. Differencing these two measurements, and correcting for errors, gives SSH typically within (± 5 cm. However these SSH measurements are the sum of the geoid (which has variability on the order of (± 90 m globally) plus the ocean (which has variability of (± 100 cm globally). Since the geoid, which for this study is fixed in space and time, is not known to the precision required for model verification, only the variability in SSH is conveniently available.

TOPEX/Poseidon data from the Intra-Americas Sea (IAS), that area of the western Atlantic which includes the Gulf of Mexico, the Caribbean Sea, the Straits of Florida and the Bahamas, are being processed to determine SSH variability. Once the three-year mean SSH is computed (1992-1995), the variability for the IAS every 10 days can be summarized. A similar calculation from the University of Miami IAS sigma-coördinates numerical model will then be compared with the SSH, and a difference field prepared. Analysis of the case-by-case and ensemble differences give vital clues as to the ability of the Miami model to replicate variability in the IAS region.

In addition to verifying models, the SSH data per se have intrinsic applicability to Florida Bay science. For example, it is now thought that variability of the Gulf Loop Current, which is the source of the Florida Current, can be traced upstream to perturbations in the Caribbean Current. Thus some of the events in Florida Bay may be associated with happenings external to the Straits of Florida and indeed to the IAS itself. It is these teleconnections that investigation of SSH from TOPEX/Poseidon is expected to clarify as well as (ultimately) providing constraint to numerical models themselves.

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A Mass-Balance Model of Salinity in Florida Bay: A Tool for Research and Management

W.K. Nuttle, J. Fourqurean, Florida International University; B.J. Cosby, J.C. Zieman, University of Virginia.

FATHOM is a 2-D, transient, mass balance model for water and salt in Florida Bay. The term "model" does not, however, entirely describe the focus of this project. Our goal is not simply to produce a computer code that can simulate present conditions and forecast future conditions in Florida Bay. Rather, toward the broader goal of understanding of the processes controlling water salinity and circulation in Florida Bay, we are working to produce a conceptually simple, computationally efficient code that is accessible to a broad audience of researchers and managers.

Background

A simple accounting of the water budget for Florida Bay reveals the root cause of episodes of high salinity, which have been linked with perceptions of a general ecologic decline. In an average year direct evaporation from the Bay entrains and concentrates sea water from the Gulf of Mexico resulting in generally hypersaline conditions. Evaporation is by far the largest flux in the water budget; the precise figure is not known, but it is believed to be between 150 cm/year and 210 cm/year over the 2.2 109 m2 surface of the Bay. During the period 1980-1989 by comparison, direct precipitation on the Bay was around 120 cm/year, and freshwater runoff via Taylor Slough and the C111 Canal was only about 8 cm/ year on average. Precipitation and freshwater runoff may exceed evaporation for short periods within a year, reversing the direction of net advective exchange with the Gulf, flushing hypersaline water from the Bay. In rare wet years, this flushing can maintain salinities below 30 ppt throughout the Bay for extended periods; such an event is currently underway.

At slightly finer temporal and spatial resolution, patterns of salinity in the Bay are determined by hydrodynamic mixing and stochastic variations in freshwater fluxes. Under normal, hypersaline conditions, salinity is determined by the rate of hydrodynamic mixing, which drives a seaward flux of salt by dispersion. This mixing is probably dominated by tides, including residual currents. However the relative contribution of lower frequency processes, i.e. direct and remote wind forcing and sea level fluctuations, has yet to be established. During extended periods of excess freshwater flow over evaporation, the net flux by hydrodynamic mixing reverses to balance advection of salt, now out of the Bay. The occurrence and intensity of these freshet events depends critically on the magnitude of variations in freshwater flows and their timing relative to the variation in evaporation.

Objectives

The main question facing managers is "To what extent have hydrodynamic mixing and freshwater flows been altered by human activities in the Bay and upstream in the Everglades?" A related question is

http://www.aoml.noaa.gov/flbay/circ95.html (7 of 20)9/10/2007 2:32:34 PM Circulation Models & Tides-1995 "What will be the effect of future activities?" These questions cannot be answered without some basic research. The objectives for research must be 1) to identify processes that control hydrodynamic mixing and the magnitude and timing of variation in the water balance fluxes in Florida Bay, and 2) to establish the degree to which these processes are sensitive to activities that have occurred and those that may occur in the future. Widely recognized is the need for a model that can be used to interpret data related to mixing and circulation in Florida Bay. A calibrated version of such a model could be used by managers to explore implications of the available data. The model must be physically-based, in order to justify extrapolation from current data, and an uncomplicated model structure is justifiable due to the limited quality and quantity of data describing Florida Bay. Also, a conceptually simple model is more accessible to a broad audience of scientists and managers.

Modeling Approach

FATHOM can be understood as a refinement of the mass balance accounting described above for all of Florida Bay. In the model, the Bay is divided into approximately 40 cells based on the location of prominent shoals and banks. A running account is kept of the mass of water and salt in each cell; precipitation is added, evaporation is lost, and fluxes of water and salt between cells are calculated as described below. The cells are assumed to be well mixed for the purpose of estimating salinity. In addition, freshwater runoff is added to cells along the northern boundary of Florida Bay, and water levels are varied to simulate tides along the Gulf of Mexico and Atlantic Ocean boundaries. Hydrologic fluxes vary monthly following the mean annual cycle for each component, and tides vary harmonically with semi-diurnal, fortnightly and annual cycles represented.

A key assumption of our approach is that mixing is instantaneous within cells and that mixing between cells is by tide-driven advection across the intervening banks, which are also the primary control on water movement. Fluxes of water and salt across a bank are calculated from the instantaneous water level in each cell, the depth distribution along length of the bank and the salinity of the upstream cell. Velocities on either side of the bank are assumed to be zero; therefore the difference in water levels is the potential energy, or head, available to the flow. This head difference is partitioned between energy loss due to bed friction and velocity head, which is dissipated by flow into the downstream cell. If the head difference across the bank is extreme, or if the water level in the downstream cell drops below the top of the bank, the bank will behave as a weir with critical flow occurring at the downstream edge. These conditions are sufficient to calculate a flux per unit length of bank for any combination of upstream and downstream water levels and depth distribution.

FATHOM runs on a moderately endowed PC. An interactive shell provides the user with access to all inputs and parameters to set up and run a simulation, and the same shell allows for selective viewing of simulation results. Bathymetric data for the cells and bank are derived from a GIS file of digitized elevations, which can be updated readily as better data become available. The user can also change the configuration of the cells and the depth distributions along individual banks prior to running simulations. Files of daily values of runoff, precipitation and evaporation can be attached as an alternative to the monthly average values generated internally.

http://www.aoml.noaa.gov/flbay/circ95.html (8 of 20)9/10/2007 2:32:34 PM Circulation Models & Tides-1995

Summary of Results to Date

A series of baseline simulations have been performed of the annual cycle of monthly salinity distributions in Florida Bay. Simulation of an "average" year is based on average monthly hydrology in the region for the period 1980 to 1989 and the "average", predicted tides. "Wet" year and "dry" year simulations are based on varying the precipitation and runoff into the Bay by 50 percent. For comparison to actual, observed conditions, we have identified "average", "wet", and "dry" years in the monthly water quality monitoring data covering the period 1989 to present. Overall, the results are very encouraging. With essentially no calibration, FATHOM reproduces the overall range and the broad spatial pattern of observed salinity.

Outlook For Remaining Work

The existing code is inadequate for the experimental studies for which FATHOM is intended. For example, the current version of the model is not parameterized to include the effect of wind stress on circulation in the Bay; neither has the tide-driven mixing in the model been calibrated against historical data on water levels and salinity. These and other deficiencies were largely a concession to the amount of time allotted for the development of the code and lack of readily available data. The recognized deficiencies must be addressed before FATHOM can be used to investigate the questions that are of direct interest to resource managers.

There are four objectives for further work. First, we propose to address recognized deficiencies in FATHOM by extending and refining the computer code. Second, we propose to use the model to investigate some of the issues relating to the management of water fluxes into Florida Bay. This will entail 1)a systematic exploration of the influence of various factors on salinity in the Bay through a sensitivity study conducted with the model, 2)calibration of the model against the available historical data, and 3)exploration of the impacts of changes in the morphology of the basin and freshwater flows. Third, we propose to integrate FATHOM with an existing program to monitor water quality in Florida Bay. Finally, we foresee further development of the model to allow simulation of nonconservative solutes, i.e. nutrients, in the Florida Bay system.

As part of a monthly water quality monitoring program, FATHOM could be used to "forecast" changes in water quality based on the latest water quality observations in the Bay and data on runoff and climate for the intervening period. The model forecasts would anticipate the onset of critical patterns of salinity and other events of interest, the occurrence of which could be tested by the next set of data collected. Over time, experience accumulated from a number of cycles of model extrapolation and testing by observation will inevitably lead to insights suggesting improvements to both the model and the monitoring program and possibly new areas of research.

A Preliminary Modeling Study of Circulation and Transport in Florida Bay

http://www.aoml.noaa.gov/flbay/circ95.html (9 of 20)9/10/2007 2:32:34 PM Circulation Models & Tides-1995

Y. Peter Sheng, Justin Davis, Yingfeng Liu, Coastal & Oceanographic Engineering Department, University of Florida, Gainesville, Florida 32611.

A preliminary modeling study on the circulation and transport in Florida Bay has been conducted. The study includes: (i)A preliminary review of the available data from Florida Bay, (ii)A preliminary model simulation of Florida Bay circulation, and (iii)A recommendation on the development of a comprehensive model of Florida Bay which can be used to aid the management/restoration of Florida Bay.

A set of high resolution (20 meters x 20 meters) bathymetric data for Florida Bay were obtained by the Everglades National Park. A comprehensive set of data were also obtained at numerous stations in Florida Bay 1993 and 1994 by the Everglades National Park. These data include water depth, temperature, conductivity, and rainfall. On the contrary, evaporation data were obtained at 1-2 stations only. There were only limited wind and tide data from the offshore waters to the south of Florida Keys. Freshwater discharge data are particularly lacking. Although discharge data are available at 3-4 flow structures upland from the Panhandles, there exists little data to indicate how the freshwater flows into Florida Bay.

Using the data indicated above and a 3-D curvilinear-grid model developed by Sheng (1987, 1989, 1994), we conducted preliminary model simulations of tidal, wind-driven and density-driven circulations in Florida Bay. The simulation results, obtained in the curvilinear grid shown in Figure 1 indicated that the model is capable of simulating many of the observed circulation features in Florida Bay, including tidal amplitude (Figure 2), tidal phase, residual circulation, hypersalinity due to evaporation (Figure 3), and lowering of saline due to freshwater inflow. Two other circulation Natures in Florida Bay: the flooding and drying of mudbanks during periods of high wind and tide and the effect of mangrove vegetation on circulation, can also be simulated by the model Al tough results are not completed for Florida Bay simulations.

To develop a comprehensive circulation model of Florida Bay, it is feasible to include all of the above mentioned model features in the 3-D curvilinear grid model used in this study or another similar circulation model. In addition, it is necessary to incorporate a robust air-sea interaction scheme into the circulation model to improve the estimation of wind stress, heat flux, rainfall, and evaporation flux at the air-sea interface. One possibility is to couple the circulation model with a regional scale atmospheric circulation model which includes a robust marine boundary layer model.

Florida Bay circulation is also influenced by (l)freshwater inflow from the Everglades area to the north of the Bay, (2)tides and circulation in the Western Florida Shelf, and (3)tides and circulation in the Florida Strait. A study, which may include the use of a groundwater flow model, is needed to quantify the freshwater inflow into the Bay. A comprehensive modeling study to incorporate the influences of Western Florida Shelf and Florida Straits on Florida Bay is presented in this report.

The Florida Bay circulation model can be coupled to a water quality model and a seagrass/light

http://www.aoml.noaa.gov/flbay/circ95.html (10 of 20)9/10/2007 2:32:34 PM Circulation Models & Tides-1995 attenuation/epiphyte model to study the effect of altered freshwater discharge schemes on the circulation, water quality and seagrass in Florida Bay. Such a coupled model has been developed for other shallow estuaries in Florida. Similar approach may be adapted for the development of a comprehensive modeling system for Florida Bay.

Acknowledgment

The work reported herein has been supported by the National Park Service, Everglades National Park and Dry Tortugas National Park. Robert Brock served as the Project Officer. Dewitt Smith provided all the hydrodynamics and hydrologic data. Jim Fourqurean and David Rudnik provided the water quality data. Ned Smith provided his results of harmonic analysis.

Florida Bay Circulation

Ned P. Smith, Harbor Branch Oceanographic Institution, 5600 U.S. Highway 1 North, Fort Pierce, Florida 34946.

Historical data obtained since the early 1980s from waters surrounding Florida Bay provide a valuable regional framework for designing studies conducted within the bay itself, and for interpreting data collected from those studies. An eleven-month time series of mid-depth current speeds and directions was obtained at a study site 48 km west of Cape Sable during 1984-5. Results indicated well-defined tidal ellipses with the major axes oriented in an east-west direction. Low-frequency nontidal flow past the study site was consistently toward the southeast or east-southeast, i.e., directly into Florida Bay. The long-term resultant current speed was approximately 4 cm s-1.

Current meter data from the 81°05'W meridian were collected as part of a Florida Department of Environmental Protection sponsored study to define regions of nontidal inflow and outflow along the western boundary of the bay. During a 12-month period starting in March 1994, the net flow patterns at three locations equally spaced between East Cape and Marathon were quite different. At the northern study site (25°05'N), nontidal outflow was recorded from mid June to early October. This was followed by a period of persistent inflow from mid October through the end of the record in early April. At the central study site (24°57.5'N), a quasi-steady flow into the bay was recorded for the entire 386-day time period. Flow past the southern study site (24°50'N) alternated between south-southwestward and northwestward, but the resultant flow was west-northwestward, out of the bay. Results of this study confirm an active and persistent exchange of water between Florida Bay and shelf waters of the eastern Gulf of Mexico, but the spatial variability cannot be resolved with only three study sites.

Along the eastern and southeastern fringe of Florida Bay, long-term net flow patterns have been

http://www.aoml.noaa.gov/flbay/circ95.html (11 of 20)9/10/2007 2:32:34 PM Circulation Models & Tides-1995 established by mooring current meters in the major tidal channels that connect Florida Bay with Hawk Channel on the Atlantic side of the keys. Seven tidal channels in the Upper and Middle Keys have been investigated over the past five years. Results from Tavernier Creek are inconclusive at this time. During a 97-day study period from mid June through mid September 1994, the net flow was into Florida Bay from the start of the study through mid August, then out of the bay through the end of the study period. The data may reveal part of a seasonal pattern, but the net flow past the current meter for this specific time period was nearly zero.

Data from Snake Creek and Whale Harbor Channel collected during the latter part of 1994 and early 1995 reveal an anomalous, though probably local condition in which the long-term nontidal flow is out of Hawk Channel and into Florida Bay. Data from Snake Creek, collected from July 1, 1994 to January 3, 1995 indicate an inflow with a resultant speed of 5.4 cm s-1. Current meter data from Whale Harbor Channel (adjacent to Snake Creek on the Key West side) collected from September 20 to December 13, 1994 show a net inflow with a resultant speed of 7.6 cm s-1.

Data collected within the past several years at all other major tidal channels show a net outflow from Florida Bay. A 118-day time series (September 22, 1994 to January 18, 1995) from Indian Key Channel revealed a resultant 4.4 cm s-1 outflow into Hawk Channel. Similarly, a 178-day time series (January 28 to July 25, 1994) from Channel Two indicated a 4.1 cm s-1 resultant outflow. Data from Channel Five collected between August 3, 1990 and January 3, 1991 showed a resultant outflow of 2.9 cm s-1, but this record appears to include two components of a seasonal cycle. Outflow during the first part of the study period was over three and a half times faster than outflow from late September through the end of the record. The longest time series come from Long Key Channel, and these records are well suited for defining low-frequency variability over seasonal time scales. A 415-day time series (July 1, 1992 to September 9, 1993) showed a resultant outflow of 2.6 cm s-1, but outflow was strongest during winter and early spring months. More recently, a 319-day study from the same location in Long Key Channel indicated a resultant outflow of 4.9 cm s-1, but again the strongest outflow occurred in winter months.

With the above as background, a one-year circulation study was initiated within the Everglades National Park part of Florida Bay. The principal objective of the study was to quantify tidal exchanges and the long-term net transport through three major tidal channels connecting sub-basins in the western part of the bay. Current meters were moored in Conchie Channel (starting July 26, 1994), Iron Pipe Channel (starting August 9, 1994) and Man of War Channel (starting August 30, 1994). Water depth in all three channels is approximately 3 m, and current meters were moored just below mid depth and in mid channel. Current meters record speed, direction and water temperature hourly. The analytical methodology includes harmonic analysis to quantify amplitudes and local phase angles of the principal tidal constituents, the calculation of cumulative net displacements past the current meter, and the calculation of total volume transport through the channel cross-section. Displacement is calculated by multiplying the along-channel current speed by the one-hour time interval it represents. Net displacements are obtained by defining outflow to be positive, and cumulative values are obtained by summing hourly displacements.

The study design calls for leaving the current meters in place until mid September, 1995 to obtain a one-

http://www.aoml.noaa.gov/flbay/circ95.html (12 of 20)9/10/2007 2:32:34 PM Circulation Models & Tides-1995 year record from each location. Data collected to date shows a persistent nontidal out-flow at each of the three study sites. Outflow from Conchie Channel (July 26, 1994 to April 5, 1995) averaged 2.3 cm s-1 during this 253-day time period. Low-pass filtered current speeds are generally within the range of 0-5 cm s-1, and low-frequency flow into the bay for more than a day or two at a time is rare. The co- oscillating tidal current superimposed onto the net outflow is substantially stronger. The amplitude of the semidiurnal M2 constituent is 32 cm s-1. Results from Iron Pipe Channel are significantly different only in the sense that both the resultant speed and the amplitude of the M2 tidal current are much higher. During the 239-day period from August 9, 1994 to April 5, 1995, the mean outflow averaged 13 cm s-1. Harmonic analysis of the time series indicates an M2 amplitude of 56 cm s-1. Low-frequency nontidal flow is generally between 10 and 20 cm s-1, and low-frequency inflow appears only five times during the study period. Data from Man of War Channel indicate a weaker resultant outflow of just under 9 cm s-1, but the amplitude of the M2 tidal constituent is 57 cm s-1. Low-frequency nontidal currents are largely between 5 and 15 cm s-1.

The remaining work for this study focuses upon the causes of the observed net outflow through the three tidal channels in the western part of the bay. It is logical to assume that some fraction of the Bay-to-Gulf outflow is a response to regional wind forcing. Similarly, it is likely that at least a portion of the outflow may be traced back to fresh water entering Florida Bay along its northern boundary. A third possibility involves a response to tidal forcing. The tidal "pumping" effect (the difference between transport during the flood tide and transport during the ebb tide) results in a net transport in the direction of the tidal current at the time of high water. Along the western side of Florida Bay, highest water levels coincide closely with strongest flood tide speeds. The magnitude of residual tidal transport is inversely related to water depth, because the frictional force resisting flow at low tide is especially large when the water is shallow. Thus, one would expect a pronounced transport into the bay associated with tidal waves converging into the shallow interior. Tide-induced transport across the shallow mud flats will set up water levels in the interior, and tidal channels will serve as a path of least resistance for the compensating return flow. This process will enhance the ebb tide in tidal channels that connect the interior of the bay with adjacent coasal waters. If the low-frequency outflow through the tidal channels is coherent with the time-varying amplitude of the tide along the western boundary of the bay, this will support the alternative hypothesis that the net outflow may be a local return of water pumped into the bay over each tidal cycle.

In the final weeks of this one-year field study, we will attempt to sort out the relative importance of wind and tidal forcing. Current meter data will be analyzed with wind stress data (calculated from observations made at the C-MAN weather station northwest of Long Key), and the coherence of wind stress and nontidal outflow will be compared with the coherence of tidal forcing and nontidal outflow. Results of the Florida Bay circulation study should put in sharper focus the relative importance of forcing by winds, tides and (as an unexplained residual) surface runoff. The relative importance of alternate forcing mechanisms will be useful in deciding what kind of forcing has to be included in any modeling effort that is to be undertaken to guide management decisions.

http://www.aoml.noaa.gov/flbay/circ95.html (13 of 20)9/10/2007 2:32:34 PM Circulation Models & Tides-1995 Automated In Situ Monitoring of Meteorological and Oceanographic Parameters on the Florida Keys Coral Reef Tract and in Florida Bay

S.L. Vargo, J.C. Ogden, Florida Institute of Oceanography, 830 First Street South, St. Petersburg, Florida 33701, USA; J.C. Humphrey, Keys Marine Laboratory, P.O. Box 948, Layton, Florida 33001, USA .

The Florida Institute of Oceanography (FIO) operates six enhanced Coastal Marine Automated Network (C-MAN) SEAKEYS stations designed and installed under a cooperative agreement with the NOAA National Data Buoy Center (NDBC) as part of a major long-term monitoring program encompassing the 220 mile long Florida reef tract. The SEAKEYS stations are located at five sites along the reef tract (Fowey Rocks, Molasses Reef, Sombrero Reef, Sand Key, and the Dry Tortugas) and one site in Florida Bay approximately 2.25 miles NW of Long Key (24° 50' 36" N, 80° 51' 42" W). The Florida Bay station was installed in November 1992 and is located immediately adjacent to the southwest boundary of Everglades National Park. The SEAKEYS stations record meteorological (wind speed, direction, and peak gust; barometric pressure, air temperature, and solar irradiance) and oceanographic (temperature, salinity, and submarine irradiance at 1 and 3 m water depth) data. The Florida Bay station has one set of oceanographic sensors at 1 m depth as the overall water depth is only 2.2 m. The data are transmitted from the stations via GOES satellite, are formatted, verified, and archived by the NDBC and are downloaded by the FIO in near real-time by telephone modem from the Data Collection Automatic Processing System (DAPS) in ASCII machine language and processed with D-Base software. Data are also made available to more than 30 institutions, agencies, and individuals via fax and Internet under a cooperative agreement with the NOAA Atlantic Oceanographic and Meteorological Laboratory (AOML) in Miami.

During the first year of operation (11/6/92 - 12/31/93) data from the Florida Bay station documented a number of environmental events. During November and December 1992, the water clarity index decreased to 10% due to the presence of the algal bloom which developed in Florida Bay after Hurricane Andrew. Water clarity increased rapidly as the bloom moved off the site, then declined rapidly again when the bloom returned on 12/10/93. Cold fronts passing through the area resulted in drops in both water temperature ( 4°C) and salinity ( 4 o/oo). These changes in temperature and salinity persisted for 4- 7 days after passage of the front. These rapid declines in water temperature (>5°C over 24 hrs) were again apparent during the "Storm of the Century" on March 13-14, 1993. In the summer of 1993, temperatures ranged from 29 - 33° C and salinity from 33 - 37.5 o/oo. Again wind events were very important. Temperature decreased with increased wind speeds. Salinity was not strongly affected by increased wind speeds. A 4.5 o/oo decrease in salinity in mid-September is probably related to the Mississippi flooding in late summer 1993. Drops in salinity during this period were found at all the SEAKEYS station but the pattern was complex.

Comparing the data from 1992-1993 with the data from January 1, 1995 - August 26, 1995 similar patterns are apparent. Salinities ranged from 28 - 36 o/oo and temperatures from 15 - 33°C. Salinities and temperatures were lowest from January - March 1995. Overall the salinities were lower than those

http://www.aoml.noaa.gov/flbay/circ95.html (14 of 20)9/10/2007 2:32:34 PM Circulation Models & Tides-1995 recorded 1993 (range 33 - 39 o/oo). These decreases in salinities may reflect the increased rainfall in south Florida during 1995. It is important to note, however, that despite the increased rainfall salinities were consistently higher (33-36 o/oo) from June - September 1995 during the peak of the rainy season than during the drier period from January - March (28 - 34 o/oo). Due to the areal extend and shallow depths in Florida Bay, evaporation at higher air and water temperatures in the summer may be a major factor influencing salinity. Wind events were also important. Increases in wind speed were followed by decreases in water temperature in both winter and summer. Again there was no apparent effect of wind on salinity.

The data from the SEAKEYS Florida Bay station demonstrates clearly the highly variable physical and biological factors in this shallow water region which must considered in developing monitoring plans to detect environmental changes which may result in management actions.

Salinity and Current Patterns in Western Florida Bay

John D. Wang, Applied Marine Physics, Rosenstiel School of Marine and Atmospheric Science University of Miami; Thomas N. Lee, Meteorology and Physical Oceanography, Rosenstiel School of Marine and Atmospheric Science, University of Miami.

Introduction

It is widely believed that water quality conditions have changed gradually in Florida Bay over the past several decades. The recent extensive sea grass dieoffs and algal blooms are indications of such changes. When seeking causal processes for these changes, reduced runoff from the Everglades and pollutant influx from the west inevitably are raised as significant problems. Resolution of these issues requires that the hydrodynamics circulation response in the Bay be quantified. The transport fluxes across the western boundary of the Bay and through the channels between the Florida Keys are potential major input and output functions and deserve particular attention.

With support from the Florida Department of Environmental Protection, we are presently in the midst of characterizing the current and salinity patterns in western Florida Bay. This two year project began in April 1994.

Objectives

The objective of the study is to collect data on the tidal and longer term transport patterns and fluxes along the western boundary of Florida Bay and in Long Key Channel. The data collection is a cooperative effort with Ned Smith and collaborators of the Harbor Branch Oceanographic Institute (HBOI). HBOI has maintained three recording current meters along 81°05'W and one in Long Key Channel for a year long period. Our contribution is to define the spatial and temporal variability of

http://www.aoml.noaa.gov/flbay/circ95.html (15 of 20)9/10/2007 2:32:34 PM Circulation Models & Tides-1995 salinity and currents along the 81°05'W transect and to determine lagrangian trajectories. This additional information will greatly extend the usefulness of the current meter records and will allow transport fluxes to be determined with greater reliability. The results will be made available for calibration and performance evaluation of numerical hydrodynamics models of the Bay.

Methods

The study area is roughly confined to the Bay between 81°05'W and 80°50'W. The shallow water and importance of wind make accurate current meter measurements difficult. Interpolations of current meter records to compute transport is also difficult without additional information on spatial and temporal variability in currents. The 81°05'W transect was selected for installation of current meters, because the relatively deep and smooth bottom topography would more likely be associated with gentle velocity variations, and thus, would allow the current measurements to be interpolated more accurately along the boundary.

To help define spatial and temporal variability, drogues were deployed at a number of stations along the 81°05'W transect during surveys in August - September of 1994, and January - February of 1995 to sample both the summer and the winter season regimes. With vanes set at three different depths, drogues were set free simultaneously and tracked over a 30 minute period using a GPS. The brogue vanes were 25 cm high and the center of the vanes were set at depths of 20 cm, 100 cm, and 200 cm. The drogues were used in place of direct current meter measurements because of the difficulty of deploying these from a small boat in choppy seas.

Satellite tracked drifters were deployed at several locations near the 81°05'W transect and left in the water for extended periods. Of 9 drifter deployments, 6 were picked up by fishermen (and recovered), 1 stranded on Conch Key, and 2 moved offshore through Long Key Channel. The longest undisturbed deployments were for about 1 month.

In recent months we have substituted the cumbersome brogue measurements with current profile transects using an RD Instruments 600 kHz broadband Acoustic Doppler Current Profiler (ADCP). When mounted on a small boat, this instrument can collect water column current profiles while moving along a transect at up to about 4.5 knots (2.2 m/s). Transect location is obtained with a GPS. We have successfully used this instrument in depths as shallow as 1.5 m, obtaining velocities in 25 cm vertical bins about once every minute. The Long Key Channel has been surveyed on two separate days on July 21 and August 31, 1995. The northernmost and southernmost sections of the 81°05'W transect have also been surveyed on July 27-28, and August 10-11, 1995.

Salinity is often an excellent natural tracer. In 1993 lower than usual salinities helped the detection of a plume containing large amounts of water from the great Mississippi flood along the Keys and in Florida Bay. As part of the present project, we have developed an underway sampling system, which measures near surface temperature and salinity. Sampling has effectively been done at speeds up to 18 knots (9 m/ s) allowing large areas to be mapped. The sampling system consists of a Sea Bird SBE-21

http://www.aoml.noaa.gov/flbay/circ95.html (16 of 20)9/10/2007 2:32:34 PM Circulation Models & Tides-1995 thermosalinograph through which water is pumped at a rate of about 0.5 liter per second. GPS location data is added directly to the data stream from the SBE-21 using a NMEA interface box also manufactured by Sea Bird. A special bow-mounted water intake system is designed to allow high speed sampling with minimal introduction of air bubbles. The instrument sampling rate is set at 5 sec intervals.

The study area is covered by two almost 100 nautical mile long transects, which are sampled on consecutive days. By repeating these surveys at a few days interval, nearly synoptic maps of salinity are obtained. Net transport velocities can be derived from the variations in salinity patterns, and can be compared with our other observations.

Conclusions and future work

Analysis of the data and interpretation using numerical models is ongoing. Some preliminary results are listed below.

On many occasions a salinity minimum was found between least and Mid Cape (Cape Sable). Although, a number of explanations are possible, the most likely is a local source of freshwater.

The satellite drifter tracks show high visual correlation with wind direction.

Salinity maps are very useful when significant salinity gradients are present. Poor weather conditions during winter cold front passages makes it difficult to collect data closely spaced in time complicating interpretation. Although, very helpful in western Florida Bay, the salinity mapping approach would be even better suited for eastern Florida Bay due to the smaller areas extent, generally calmer sea state, and larger salinity variations.

Drogue velocities are in general agreement with current meter observations, but also indicate vertical shear effects. An additional salinity mapping period is planned for the fall of 95. Additional data quality control and analysis is also planned.

A Study to Define Model and Data Needs for Florida

John D. Wang, Applied Marine Physics, Rosenstiel School of Marine and Atmospheric Science, University of Miami; Charles Monjo, Applied Marine Physics, Rosenstiel School of Marine and Atmospheric Science, University of Miami.

Objective

This recently completed study, supported by the Everglades National Park, is aimed at exploring the potential of a 2-dimensional nearly horizontal flow model as a tool for describing the circulation in

http://www.aoml.noaa.gov/flbay/circ95.html (17 of 20)9/10/2007 2:32:34 PM Circulation Models & Tides-1995 Florida Bay. Some of the issues that the model should be helpful in addressing are the resultant changes in circulation and salinity to be expected from modifications to the freshwater runoff volumes from the Everglades, and the exchange between the Bay and the Gulf of Mexico or the Atlantic Ocean.

Methods

Several factors are considered in choosing the hydrodynamics model for Florida Bay. The primary factors are the extreme spatial complexity, shallow depths, relatively small freshwater input volumes, and the sparse set of field observations.

The study to be presented intends to define factors and processes that are important for hydrodynamics modeling of the Bay. It emphasizes methodology and data needs, but puts less emphasis on obtaining realistic (accurate) simulations, since there are not sufficient data for prescribing model forcings or for verification of model results.

The model (CAFEX) chosen for adaptation to Florida Bay is a finite element numerical solution of the vertically integrated hydrodynamics equations of motion (Wang and Monjo, 1995).

The bottom topography is obviously a very important model input for the shallow and spatially complex Florida Bay. The bottom topography data base was obtained by digitizing the NOAA/NOS Chart 11451 on a regular 15"x15" grid. The digitization in most cases simply selects the average depth value around the grid point location, but in some cases is adjusted to better represent the effective conveyance in channels between banks or islands.

The model topography is derived from the digitized data base with corrections for datum variations and subgrid scale topography. Consequently, several of the smaller islands are represented as very shallow areas in the model because of their size. We have not attempted to fine tune the model topography to features, which are of the order of the grid point spacing or finer. Such fine tuning will be more productive, when grid resolution can be refined, and when more current observations are available.

The drying and wetting of semi-submerged banks, because of their expansive extent, are likely to be extremely important processes controlling the circulation patterns in Florida Bay. The banks block flow entirely, when the water level is sufficiently low, and bank overflows are subject to strong nonlinear effects due to friction. These processes are incorporated into the model.

Because of the time consuming and data intensive effort to include the actual geometry and topography of the Keys channels, these have simply been included as openings in the model. The size of the openings somewhat reflect the actual width of channels, but is also controlled by the local grid size. A better definition of the channels will require a locally finer grid resolution, detailed current and water height observations, and may even require a separate model component to interface with Atlantic open coast tides.

http://www.aoml.noaa.gov/flbay/circ95.html (18 of 20)9/10/2007 2:32:34 PM Circulation Models & Tides-1995 Seventeen different runs using a grid of 6143 elements and 3205 nodes illustrate the response of the CAFEX model and its sensitivity to input parameters. Many more runs were made to better define realistic parameter ranges. The variable input include the amplitude and phase of the tide on the western boundary, bottom friction, wind, density fore g, between Keys channel flow, and fresh water input from the Everglades.

Numerical results are displayed in several formats. Velocity field plots show the computed velocities in Florida Bay on an approximately 2 km grid (at the centroid of every fifth triangular element), at an instant in time.

Time series plots give a detailed picture of velocity vectors, water depth, and separate (u, v = east, north) components of velocity as a function of times but at a fixed location. This presentation method is particularly well-suited for comparison with data time series. Particle trajectory plots show the track of a water particle over a 30 day period as a simulation of the lagrangian path followed by a water borne substance. Another way of demonstrating the transport and mixing is through a plume simulation obtained as a solution of the advection-diffusion equation.

Results and Conclusions

The results indicate a western zone strongly influenced by Gulf of Mexico tides and with a tidally driven southeasterly mean flow. The central and eastern Bay zones are much less affected by tides and thus more strongly influenced by wind.

The channels through the chain of Florida Keys appear to have important implications on circulation in all parts of the Bay and additionally transmits Atlantic Ocean tides to a region close to the Keys. At least toward the southwest, these channels also serve as relief valves for the Gulf of Mexico tides, thereby reducing their effects in the interior and eastern Bay.

Many model parameters are important to the long and short term dynamic response, including boundary tides, friction, Keys channel transports, and wind. The freshwater runoff from the Taylor Slough area of the Everglades is only moderately important for long term transports and only in eastern Florida Bay and during calm-wind conditions. We have not made simulations with a mean sea surface slope between open boundaries, however, experience has shown that even a small sea level difference, as may be caused by strong ocean current systems, will have a strong effect on mean flows. For accurate model predictions, all these parameters must obviously be reasonably quantified.

The parametric studies showed that the physical processes in the model appear capable of describing the variations in available data on currents and water depths. The main data features that the model describes with reasonable input parameters include current direction and magnitude near the western boundary of the Bay at 81°05'W and tidal height amplitudes throughout the Bay. Other features for which there is qualitative agreement include the flood flow pattern into Johnson Key basin, the tidal flow through Long Key Channels and the southwesterly mean flow into Florida Bay with associated

http://www.aoml.noaa.gov/flbay/circ95.html (19 of 20)9/10/2007 2:32:34 PM Circulation Models & Tides-1995 mean transport toward south in the Keys channels. More new observations are needed for additional evaluation of model performance.

For long term transport in Florida Bay, wind appears to have the greatest influence. The direct surface wind stress superposes a downwind velocity on tidal currents in open areas. In the eastern and central regions, local obstacles can cause recirculation cells to form, which tend to trap water masses. In the present work we have only included the direct surface stress from wind, however, many studies have shown that remote forcing and coastal waves can be important too.

A comprehensive set of data are required for model calibration and forcing. For model performance evaluation, information on lagrangian motion is the most useful. There is little hope of being able to use conventional current measurement techniques in the low velocity and complex topography areas of central and eastern Florida Bay. We have suggested mapping of salinity and dye experiments as possible ways of obtaining the required information.

Our investigations with a 2-D hydrodynamics model has not revealed any serious shortcomings in model physics based on available data. For future work, the most important improvements of the model are to obtain better forcing data and to refine the model resolution.

Wang, J.D., and Monjo, C., 1995: A Study to Define Model and Data Needs for Florida Bay. Report, Applied Marine Physics, Rosenstiel School of Marine and Atmospheric Science, University of Miami.

Last updated: 04/23/98 by: Monika Gurnée [email protected]

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Contaminants & Toxins

1995 Abstracts

Oyster and Sediment Contaminant Levels and Trends in South Florida

A. Y. Cantillo, G. G. Lauenstein, T. P. O'Connor, NOAA/NOS/ORCA, Silver Spring, MD

During the past 50 years, the South Florida ecosystem has been subject to a increase in human population and anthropogenic activity. One large environmental concern has been the reduction of freshwater flow into the Bay from the Everglades, because of drainage canals built to meet the demand for dry land imposed by increasing population and agricultural interests. Oyster and sediment samples were collected in South Florida from 1986 to 1994 as part of the NOAA National Status and Trends (NS&T) Program which is designed to assesses the current status of, and changes over time in the environmental health of the estuarine and coastal waters of the United States. Analytes quantified include 24 polycyclic aromatic hydrocarbons, 20 polychlorinated biphenyl congeners, DDT and its metabolites, 9 other chlorinated pesticides, organotins, 4 major elements, and 12 trace elements. The quality of the NS&T analytical data is overseen by the NS&T Quality Assurance Project. The concentrations of organic and inorganic contaminants in sediments and mollusks collected in South Florida from 1986 to 1994 show temporal and spatial trends that reflect anthropogenic influence in areas removed from large population centers. There is evidence of relatively high levels of man-made chemicals, such as endosulfan, at the NS&T sites in Florida Bay. High levels of Hg and As in oysters were also observed. Contaminant levels found in South Florida sites are compared to those found nationwide at other NS&T sites.

An Ecotoxicological Assessment of Pesticide and Urban Nonpoint Source Runoff into Florida Bay and Surrounding Environments

G. I. Scott, M. H. Fulton, J. R. Kucklick, National Marine Fisheries Service, Southeast Fisheries Science Center, Charleston Laboratory, PO Box 12607, Charleston, SC 29422-2607; G. Thayer, National Marine Fisheries Service, Southeast Fisheries Science Center, Beaufort Laboratory, Beaufort, NC 28516-9722.

Recent concerns about declining environmental conditions in Florida Bay, have helped focus research to address the status of living marine resources residing in the bay. The high salinity conditions now existing in Florida Bay may be in part responsible for the declining environmental conditions. Recent agreements have been reached which would increase freshwater inflows into the Everglades and

http://www.aoml.noaa.gov/flbay/cont95.html (1 of 4)9/10/2007 2:32:34 PM Contaminants & Toxins-1995 eventually into Florida Bay. Most of this increased freshwater inflow will be diverted from water management districts in south Florida, which may contain surface water runoff from a variety of sources, including urban and agricultural nonpoint sources. Thus, under this new management plan, the potential exists for pesticides and other contaminants to be released into the Everglades and be eventually discharged into Florida Bay. To address this issue, the U.S. National Marine Fisheries Service, Southeast Fisheries Science Center, Beaufort, Charleston and Miami Laboratories conducted studies to measure pesticide levels in surface water and sediments in Florida Bay and adjacent inland, agricultural watersheds. The long-term goal of this research is to assess the risk presented by water and sediment-associated contaminants in south Florida to marine and estuarine living resources.

In 1993, an initial study was conducted at 34 sites which were sampled for surface water quality measurements (temperature, salinity, dissolved oxygen, and pH) and pesticide residues (500 mL samples). Station latitude and longitude coordinates were determined by Global Position Systems (Trimble and Magellan GPSs). Several sites were also sampled for sediment pesticide levels. Stations were classified as agricultural watershed (n=6), land-sea interface (n=10), and bay stations (n=18). Additional stations were sampled in 1994 and 1995 in both Florida Bay and at inland areas near vegetable farms. The sites selected in Florida Bay were also long-term ecological monitoring sites sampled by the NMFS and Beaufort Laboratories so that ecological data from each site could be used in conjunction with contaminant monitoring data. Pesticide levels in surface waters were initially screened by polyclonal antibody test kits (triazine herbicides and cyclodiene insecticides). Samples testing positive were further analyzed for pesticides (atrazine, azinphosmethyl, endosulfan, and fenvalerate-- pesticides commonly used on vegetable farms) by capillary-column gas chromatography using both electron-capture (GC-ECD) and nitrogen-phosphorus detection (GC-NPD). Endosulfan is a supertoxic (96h LC50 for aquatic organisms < 1 ug/L) insecticide which has caused more coastal fish kills from 1980-89, than any other pesticide. Also, toxicity tests have been conducted with mosquito fish (Gambusia affinis) from different localities to assess the sensitivity of fish, which may be chronically exposed to endosulfan, in terms of cyclodiene pesticide resistance. In situ bioaccumulation and ecophysiological studies have been conducted with the oyster, Crassostrea virginica, at selected sites within Florida Bay.

Results from the 1993 study, indicated that 14.4% (5/34) of the 34 stations sampled had detectable levels of pesticides in surface water samples. Initial screening by polyclonal antibody test kit indicated detectable levels of cyclodiene insecticides (6 stations) and triazine herbicides (7 stations). Subsequent GC-ECD and GC-NPD analysis indicated only the presence of the organochlorine insecticide, endosulfan, at five stations. Endosulfan concentrations as high as 0.170 ug/L were detected. The State of Florida Regulatory limit for marine waters is 0.0085 ug/L for endosulfan. Only a few stations which had detectable endosulfan levels had concentrations that exceeded the 0.0085 ug/L state regulatory limit. Results from surface water monitoring from 1994-95 and laboratory and in situ field toxicity tests conducted to date will be discussed along with long term ecological monitoring data from sites within Florida Bay. Research planned for 1995-96 will also be discussed including planned laboratory toxicity tests on crustaceans (grass shrimp and copepods) to determine the impacts of the pesticide endosulfan, which is potentially an endocrine disrupting chemical, on survival, growth, development and reproduction.

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Monitoring Changes in the Estuaries of the United States: The Environmental Monitoring and Assessment Program in Florida Bay

J. Kevin Summers, National Program Manager, EMAP, U.S. Environmental Protection Agency, Gulf Ecology Division, Gulf Breeze, FL; John M. Macauley, Michael A. Lewis, U.S. EPA, Gulf Ecology Division, Gulf Breeze, FL

The purpose of the Environmental Monitoring and Assessment Program/ Estuaries (EMAP-E) is to estimate the current status, extent, changes, and trends in ecological indicators of the condition of the nation's coastal resources (intertidal, subtidal, and offshore) on a regional and national basis. Initial monitoring activities have been initiated or completed in approximately 70% of the nation's estuarine waters, including Florida Bay, and focus on suites of ecological measurements describing the benthic community, the fish community, water quality, levels of sediment and tissue contamination, sediment toxicity, and SAV extent/condition. Estuarine monitoring is based on a probability-based sampling design implemented over a 60-day window during July-September of each year. The use of statistical tools developed for the program show that 25% ± 4% of the sediments of the nation have degraded biological conditions while 29% ± 4% of the area show degraded conditions in relation to human uses of the resource (e.g., water clarity, tissue contaminants, and the presence of marine debris). Biological degradation is characterized by significantly less than expected number of benthic species and diversity, high numbers of pollution-tolerant species, and low numbers of pollution-sensitive species, incidence of fish pathologies, and increased levels of selected biomarkers in target fish species. Human use degradation is characterized as decreased water and sediment quality, potential for decreased consumptive use, and incidence of characteristics limiting non-consumptive use.

Monitoring and research activities in Florida Bay began in the spring of 1995 with five separate activities: (1) a baseline characterization of the ecological condition of Florida Bay, (2) a seasonal characterization of Florida Bay to examine changes in condition due to seasonal variation, (3) a characterization of the flux of materials from the primary canals and creeks draining into Florida Bay and the conditions at the mouths of these canal/creek outlets, (4) a baseline characterization of ecological condition of the terrestrial region draining into Florida Bay (Everglades National Park, Big Cypress Swamp, and the Water Conservation Areas), and (5) assistance to other existing monitoring programs in Florida Bay with regard to statistical design and analysis.

The baseline characterization of Florida Bay began in July 1995, is based on sampling at 45 probabilistic sites, and is intended to be a "snapshot" of ecological condition against which changes over the next decade can be gauged. The program focuses on sediment condition, biotic condition, level of eutrophication, and SAV condition as the primary indicators of condition. Sediment condition is measured through the use of chemical analysis of contaminants (125 contaminants including mercury and endosulfan) and basic sediment characteristics (e.g., total organic carbon, acid volatile sulfides). The

http://www.aoml.noaa.gov/flbay/cont95.html (3 of 4)9/10/2007 2:32:34 PM Contaminants & Toxins-1995 biotic condition indicators include multiple indicators of benthic communities, incidence of fish pathologies and levels of bioaccumulation of contaminants, and SAV indicators discussed below. Eutrophication is gauged by water quality parameters (e.g., light penetration and dissolved oxygen), nutrient concentrations, and productivity. Submerged aquatic vegetation condition is determined from abundance and density, abundance of epiphytic biomass, and age-structure of SAV sites. Using these same parameters, the seasonal variability of ecological condition will be described for spring-fall 1995 and winter 1996. Data from these surveys will be available in mid-1996.

The measurement of the flux of contaminants from five canals and creeks into the northeastern portion of Florida Bay consists of two time periods; summer 1995 and winter 1995-96 to characterize the wet and dry periods of runoff. The study is designed to address two primary issues: (1) Does the runoff characterized by these water bodies include significant levels of contaminants and nutrients, and (2) What are the contaminant and toxicological condition of the areas directly adjacent to the mouths of these creeks/canals. The characterization includes the C-111 Canal, Trout Creek, Shell Creek, McCormick Creek, and Taylor River. There is some discussion regarding expanding the program to include the in late 1996. Chemical results for these studies will not become available until mid-1996 but early toxicological studies suggest significant toxic responses to sediment collected from the mouths of these water outlets to plant development and the survival rates of benthic target species.

The baseline characterization of the landward system will begin in October/November 1995 and will include 75 probabilistic locations throughout the parks, natural areas, and water conservation areas. To date, we have assisted several other monitoring programs in Florida Bay to develop probabilistic sampling designs for their programs.

While little data is available as yet, EMAP Phase II will, dependent on available funding, begin: (1) the development of an intensive monitoring site network within Florida (3-5 sites) to characterize short-term mechanistic behaviors; (2) initiate direct hypothesis-testing studies to evaluate the effects of mercury and endosulfan contamination of fish, shellfish, and bird populations; (3) initiate hypothesis-testing studies to assess the effects of eutrophication and fresh-water flow reductions on the estuarine communities of northern Florida Bay, and (4) conduct intensive surveys designed to strengthen our understanding of the role of spatial scale in controlling the mechanisms of estuarine dynamics.

Last updated: 06/15/98 by: Monika Gurnée [email protected]

http://www.aoml.noaa.gov/flbay/cont95.html (4 of 4)9/10/2007 2:32:34 PM Fisheries-1995

Fisheries

1995 Abstracts

Marine Fisheries - Independent Monitoring

James A. Colvocoresses, Florida Department of Environmental Protection, Florida Marine Research Institute, South Florida Regional Lab, 2796 Overseas Highway, Suite 119, Marathon, Florida 33050; Robert H. McMichael, Jr., Florida Department of Environmental Protection, Florida Marine Research Institute, 100 Eighth Ave. SE, St. Petersburg, Florida 33701.

During the past two years the Florida Department of Environmental Protection has prioritized the implementation of its statewide marine Fisheries-Independent Monitoring (FIM) Program in Florida Bay. This program, which has been under development since 1988, uses extensive systematic scientific field surveys to assess the pre-fishery recruitment of resource species which utilize Florida's estuarine and near-coastal areas as nursery zones, as well as to generate other fishery-independent information concerning these stocks. These surveys also serve to achieve a secondary but very important objective of providing a large scale, long-term biological and ecological monitoring program in this critical area of Florida's marine environment. The program is intended to be sustained on a continuing basis and to be eventually expanded to monitor all major estuarine areas in the state.

Initial efforts in Florida Bay have focused on the development of a network of fixed sampling sites, which are being sampled monthly with beach seines and bottom trawls. Preliminary sampling began in September of 1993, with the present network of 31 permanent stations having been established as of August of 1994. Stations have been selected with the multiple objectives of meeting the fishery- monitoring goals of the overall program, providing a framework for comparing the results of present and historical sampling efforts, and for evaluating the effects of alterations of freshwater delivery schedules to Florida Bay. Sixteen sites are sampled with seines, while fifteen are sampled with trawls (Fig. 1, Table 1). The seining gear is a 70' long by 6' deep nylon-mesh, center-bag drag seine made from 1/8" #35 Delta mesh. The net is deployed over shallow flats facing into the current with brails spaced 50' apart. The net is then manually pulled a distance of 30', after which the net is closed and pursed by pulling it around a pole. The bag is then lifted and slowly inverted and the catch transferred to buckets. Deeper waters ( >1.5 m) are sampled using a 20' otter trawl made of 1-1/2" str. mesh nylon, with the bag lined with 1/8" knotless #35 Delta mesh. The trawl is towed behind a 24' mullet skiff at a speed of approx. 1.5 knots for 5 minutes. Bottom distance covered is recorded using GPS set and haul back points, and is generally about 163 m. Three spatially discreet replicate sets are made at each visit to a sampling site.

All fishes and selected macroinvertebrates are identified, enumerated, and representative length

http://www.aoml.noaa.gov/flbay/fish95.html (1 of 14)9/10/2007 2:32:35 PM Fisheries-1995 frequencies taken. Hydrographic data, atmospheric and sea conditions, and observations relative to bottom type are recorded for each collection. Temperature, salinity, pH, dissolved oxygen and conductivity are recorded at each sampling site, including both surface and bottom when depth permits discrete observations. Quantitative observations of bycatch are recorded. Direct observations of bottom type are made during seining operations, including species composition and estimated percent cover of any vegetation.

Although it is too early to draw definitive quantitative conclusions, on a bay-wide level overall initial results have shown very similar species compositions to those observed during similar studies conducted over the past thirty years, with approximately a 70% overlap in the percent species composition of the finfishes taken. On a local level, in areas where extensive seagrass loss has occurred, there appear to have been dramatic changes in community structure, with a seagrass-based community overwhelmingly dominated by rainwater killifish being replaced by a more diverse benthic fish community composed of toadfishes, gobies, pipefishes and some juvenile gamefishes such as spotted seatrout. Although undoubtedly affected by the recent ecological perturbations in Florida Bay, the finfish community may be more resilient to these changes than other, more immobile organisms.

Table 1. FDEP Florida Bay monthly fixed station sampling sites.

Sta. Gear Latitude Longitude Location

1 Offshore seine 25 14.25 80 25.38 Manatee Bay at ENP hydro station

2 Offshore seine 25 13.38 80 25.82 Manatee Bay by U.S.1

3 Offshore seine 24 54.70 80 56.31 Sprigger Bank - just S of marker '5'

4 Offshore seine 25 7.70 80 56.90 Bradley Key - W side cove

5 Trawl (6-7ft.) 25 7.12 80 56.07 MurrayKey - 1/2mi. N of key

6 Offshore seine 25 2.30 81 1.12 Sandy Key - off NW corner of key

7 Offshore seine 25 13.00 80 27.80 Shell Key - NW corner of L. Blackwater Sound

8 Offshore seine 24 55.08 80 45.25 Buchanan Bank - 1/2 mi. W of N Peterson Key

9 Offshore seine 25 5.06 80 47.30 Roscoe Key - N side of first cut S of key

10 Trawl (6-7 ft.) 25 1.15 80 33.45 Cross Bank Basin - 3/4 mi. N of marker '73'

11 Trawl (5-6 ft.) 25 4.50 80 45.15 Whipray Basin - 2 mi. N of Whipray Channel

http://www.aoml.noaa.gov/flbay/fish95.html (2 of 14)9/10/2007 2:32:35 PM Fisheries-1995

12 Trawl (6-7 ft.) 25 8.10 80 36.12 Eagle Key Basin - 2 mi. S of Eagle Key

13 Trawl (6-7 ft.) 24 57.03 80 47.52 Twin Key Basin - 1/2 mi. N of Barnes Key

14 Trawl (3-4 ft.) 25 6.00 80 52.50 Palm Key Basin - 1/2 mi. S of Palm Key

15 Trawl (3-4 ft.) 25 2.90 80 55.00 Johnson Key Basin - 1/2 mi. SW of Johnson Key

16 Offshore seine 24 58.95 80 39.00 West Key - Off beach on SE shore

17 Offshore seine 25 9.12 80 30.70 Nest Key - Off beach at campground

18 Trawl (3-4 ft.) 25 8.00 80 43.20 Crocodile Pt. - 1/2 mi. S of Pt.

19 Trawl (3-4 ft.) 25 7.50 80 48.51 Rankin Lake - 3/4 mi. W of Rankin Key

20 Trawl (4-5 ft.) 25 10.60 80 29.70 Duck Key - 1/4 mi. SE of key

21 Trawl (7-8 ft.) 24 54.65 80 39.70 Shell Key Channel - S end

22 Trawl (6-7ft.) 25 7.00 80 27.80 Buttonwood Sound - 1 mi. W of Grouper Creek

23 Offshore seine 25 4.35 80 33.30 Bottle Key - W side of N point

24 Offshore seine 25 4.45 80 38.70 Russell Key - SW shore

25 Offshore seine 24 58.10 80 51.15 Ninemile Bank opposite Rabbit Key Pass

26 Trawl (4-5 ft.) 25 0.12 80 53.80 Rabbit Key Basin at mouth of Iron Pipe Channel

27 Trawl (9-10 ft.) 24 56.70 80 57.20 Schooner Bank - 1 mi. SE by NPS marker

28 Offshore seine 24 49.10 80 52.05 Old Sweat Bank - N side

29 Offshore seine 25 11.85 80 37.15 Little Madiera Bay - mouth of E. Creek

30 Offshore seine 25 0.40 80 47.68 Sid Key Bank - bank tip 1 mi. S of SW pt. of Sid Key

31 Trawl (6-7 ft.) 24 52.25 80 52.55 Arsenic Bank - 1/2 mi. E of Yacht Channel

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Age, Growth, Mortality, Fecundity, and RNA-DNA Analysis of Spotted Seatrout, Cynoscion Nebulosus, in Florida Bay

Dana M. Elledge, Everglades National Park, Florida Bay District, 98701 Overseas Highway, Key Largo, FL. 33037; Robert J. Brock, Everglades National Park, South Florida Natural Resources Center, 40001 State Road 9336, Homestead, FL. 33034-7633.

Spotted seatrout (Cynoscion nebulosus) are currently being collected throughout Florida Bay to ascertain age, growth, mortality, and fecundity estimates along with samples being preserved for future RNA- DNA analysis. Because of the propensity of this species to spend their entire life cycle within the Florida Bay estuary, the physiological fitness of spotted seatrout may be an excellent bioindicator of changing physiochemical conditions brought about by planned changes in upstream water management practices. The goal of this research is to compare the current physiological condition of spotted seatrout with previous Florida Bay studies as well as those from other Florida estuaries.

It was estimated in 1980 that increasing demands for water in south Florida by many user groups would threaten to significantly reduce the amount of water flowing into Everglades National Park, thereby leading to the reduction of spotted seatrout populations. It was found by previous researchers that growth rates varied among spotted seatrout depending upon their location in the bay. This variation in growth rates was attributed to differences in water quality. For example, lower growth rates among spotted seatrout were found in the hypersaline areas such as western Florida Bay than in the more brackish eastern bay. The overall objectives of this project are:

Objective 1. Determine growth rates of Florida Bay spotted seatrout for contrast with other

Florida estuarine waters as well as past growth rates of this species in Florida Bay. Estimates of age, growth, and mortality of spotted seatrout will be made using samples from the recreational harvest and samples obtained by the hook-and-line method. An age regression will be constructed using otoliths to estimate growth of spotted seatrout in Florida Bay. Results will be analyzed in order to correlate a change in growth rate with recent physiochemical changes within the bay. These growth rates will also be compared to similar studies done in the past before the bay experienced the significant ecological perturbations that now exist.

Objective 2. Total weight of the ovary will be used to construct the gonadosomatic index while subsamples (0.05g - 0.10g) of the ovaries will be used to calculate fecundity. As hypersalinity becomes less common with the increase in the amount of freshwater being delivered to Florida Bay, an "improvement" in water quality will be indirectly correlated to length-weight and length-ovarian weight ratios. Fecundity estimates will be related to an age regression of spotted seatrout.

Objective 3. RNA-DNA analysis will examine the presence/absence of genetic subdivisions within the

http://www.aoml.noaa.gov/flbay/fish95.html (4 of 14)9/10/2007 2:32:35 PM Fisheries-1995 Florida Bay seatrout population. Previous mark and recapture studies indicated little inter-estuary movement. Gill arches and subsamples of the caudal fin are being frozen for future RNA-DNA analysis. Results from three distinct physiographic areas within Everglades National Park (Ten Thousand Islands, western Florida Bay, eastern Florida Bay) will be compared. Results will also be compared and contrasted with similar work being done in other Florida estuarine waters.

Fishery-dependent and fishery-independent samples are being collected monthly all over Florida Bay. Data recorded for all samples include date of capture, area captured, total length, total weight, sex, gonad weight, and physiochemical parameters such as water temperature and salinity. 534 otoliths have currently been extracted for future age and growth analysis. 350 gonads have been weighed in order to construct a gonadosomatic index. 100 ovaries have been subsampled to estimate fecundity and 65 gill arches have been frozen for future RNA-DNA analysis.

Collection of samples will continue until approximately September, 1996.

Assessment of Trophic Structure, Mercury Levels, and Responses of Fish and Shellfish to Changes in Habitat in Florida Bay

Donald E. Hoss, Gordon W. Thayer, NOAA/NMFS Beaufort Laboratory, Beaufort, North Carolina 28516-9722.

Investigators at the NMFS Beaufort Laboratory are conducting research to address the interagency Florida Bay Science Plan. Our objectives deal with changes in the distribution and abundance of living resources that have occurred in the Bay, including changes in trophic structure and effects of toxic pollutants on target organisms. Research efforts include sampling with various gear types for phytoplankton, zooplankton, ichthyoplankton and juvenile fish. Sampling was initiated on a monthly to bimonthly basis beginning in September 1994. Ichthyoplankton and zooplankton data, once analyzed, will be compared with data collected by us in 1984-1985 using similar sampling protocols and stations. Benthic habitat, and the resident fish community structure are being analyzed from data collected on a bimonthly bases, beginning in July 1994, using the same stratified random-sampling stations employed during 1984-1985. Mercury/methylmercury analyses will be made on target carnivore fishes (e.g., red drum, spotted seatrout, and gray snapper) and their food sources beginning in fall 1995. This study is being funded by the NOAA Florida Bay Restoration Program, and we project continued field sampling, laboratory analyses, and data syntheses throughout calendar years 1996 and 1997, with expansion of efforts in future years.

Data analyses are progressing on all aspects of the project. Presently, our ichthyoplankton samples are being sorted with an emphasis placed on spotted seatrout larvae, a species that we regularly collected in 1984-1985. Analyses of water samples for enumeration of phytoplankton indicate a minimum of 27 common genera including centric and pennate diatoms, monads, dinoflagellates and flagellates. There

http://www.aoml.noaa.gov/flbay/fish95.html (5 of 14)9/10/2007 2:32:35 PM Fisheries-1995 are both geographic and seasonal signals in the phytoplankton with spatial influences dominating temporal ones. The eastern region of Florida Bay is characterized by low phytoplankton biomass; the central region, and especially the north-central, is a seasonally influenced productive area; and the western portion of the Bay is also productive, but less influenced by seasonal changes.

Assessments of the fishery habitat and fishery community demonstrated consistent decreases in both plant and fishery species abundances relative to 1984/85. Thalassia, Syringodium, and Halodule short shoot densities have decreased extensively in each of the four strata that were sampled in 1984/85. Fish densities have decreased dramatically in Johnson Key Basin and in areas adjacent to Gulf of Mexico waters and channels within Florida Bay, but show little numerical change in areas adjacent to the Atlantic Ocean and an actual increase in the central portion of our sampling area. In the central portion, there has been a shift in the dominance of resident fishes from mojarra and rainwater killifish during 1984/85 to bay anchovy during July 1994 - May 1995, and the increases observed in the Central stratum were due to increases in bay anchovy at those stations where seagrass habitats were impacted. Since anchovy are an important food resource for spotted seatrout, any increases in anchovy numbers may have a positive influence on spotted seatrout abundances. This shift in resident fish dominance also suggests a shift in trophic feeding levels. Mojarra are benthic feeders and rainwater killifish feed on crustaceans associated with the seagrass canopy while anchovy are water column particle/zooplankton feeders.

The Effects of Hydrology on Fish Species of the Florida Bay Mangroves Zone: Preliminary Results

Jerry Lorenz, Chris Harrington, National Audubon Society.

The mangrove-dominated zone that forms the interface of the Everglades with Biscayne and Florida Bays is an important area for wildlife in south Florida. This polyhaline dwarf red mangrove (Rhizophora mangle) swamp provides a primary nursery ground for sport fish, is the primary habitat of the endangered American Crocodile and West Indian Manatee and is heavily used as a feeding ground by wading birds. Historically freshwater from the Everglades reached the Florida Bay mangroves via Taylor Slough. In recent decades, the hydrology of the mangrove zone has been altered by the construction and operation of a system of canals and levees. Outstanding among these is the C-111 canal, which diverts water from Taylor Slough to an area just east of US Highway 1, thereby disrupting the natural processes in both areas. Further complicating the freshwater flow pattern is the US Highway 1 levee which has blocked all surface water flow from the Everglades to Biscayne Bay.

There is a great deal of evidence that indicates a change has occurred in the types of plants growing in this region coincident to the changes in water delivery. We believe that prey base fish populations have also been affected by these changes in hydrology and flora. Our current thinking is that water management practices in the Everglades, specifically management of the C-111 canal drainage area,

http://www.aoml.noaa.gov/flbay/fish95.html (6 of 14)9/10/2007 2:32:35 PM Fisheries-1995 adversely affect the populations of small fishes in the mangrove zone and, as a result, may be implicated in the decline of wildlife throughout the Florida Bay region.

Sampling fishes in this area proved to be somewhat of a challenge. Deep mud, unforgiving climatic conditions and myriad biting insects combined to drive away all but the most determined scientists. Furthermore, accepted techniques for sampling fishes over wetlands all proved flawed in this unique habitat. Eventually, through trial and error, a unique nine square meter drop net that effectively collected mangrove fishes was developed. This method requires little contact with the substrate, does not alter the habitat being sampled, does not alter the distribution of fishes over the wetland surface, and allows for differential sampling of microhabitats within the wetland. Catch efficiencies range from 78% for rainwater killifish Lucania parva to 92% for gulf killifish Fundulus grandis.

To accomplish our goal of linking manmade changes in water delivery to resident species abundance, we sampled fish populations in the mangrove zone of Biscayne and Florida Bays from 1990 through June 1995 at four to six week intervals, in conjunction with a detailed analysis of hydrologic conditions through the use of continuous recorders. Sites were selected based on the proximity and hydrologic influence of Taylor Slough. The three sites north of Florida Bay were selected based on a decreasing west to east gradient of the influence of the Slough, with TR (located in central Taylor Slough) receiving the most fresh water, HC receiving the least and JB intermediate between the two (JB and HC were sampled August 1990 - June 1995 and TR from December 1991 - June 1995) . BS (sampled from February 1992 - June 1995), located on Barnes Sound, historically received some freshwater from the Everglades, but the construction of US-1 and Card Sound Roads had impounded the area, effectively cutting off all surface connection to the Everglades. A site on Cape Sable (BL: sampled from August 1990 - present) was selected as a reference site in that it is probably the area least influenced by direct water management activities. Two sites associated with the freshwater Slough (9M: November 1993 - June 1995 and MD: October 1994 - June 1995)) were not sampled until late in the study and will not be addressed here. Furthermore, space restrictions dictate that data collected at BL, although pertinent, will not be discussed.

Preliminary numerical analysis of the first three years of our data set indicate that prey fish density and biomass are adversely affected by lower rates of fresh water inputs. Categorizing the years based on rainfall data, the first year was a drought year (1990-1991) the second year (1991-1992) had close to "normal" rainfall and the third year (1992-1993) had higher than normal rainfall and can best be described as a flood year. Hydrologic data indicate that the percent of high water days increased yearly from the drought year to the flood year Furthermore the percent of high water days decreased from TR to HC, along the west to east gradient of Taylor Slough influence (an exception was the unexpectedly high water at HC during the drought year). Likewise, the percent of low salinity days increased from the drought year to the flood year and decreased across the west to east gradient.

Resident fish of the mangrove swamp responded to the spatial and temporal changes in water delivery. The periodic sample with the highest estimated biomass increased from the drought year to the flood year and decreased from west to east along the decreasing freshwater gradient. The implications are that decreased flow over the last 30 years may have eroded the food pyramid of the Florida Bay ecosystem

http://www.aoml.noaa.gov/flbay/fish95.html (7 of 14)9/10/2007 2:32:35 PM Fisheries-1995 from the bottom up, thus culminating in the current decline of top predators such as wading birds and game fishes. However, a complete analysis of the data set must be performed in order to confirm these preliminary results.

Another goal of the study was to examine the effects of introduced fish species on the native fauna. The exotic Mayan cichlid (Cichlasoma urophthalmus) was the most common species collected by weight and made up as much as 90% of the catch by biomass in some samples. Prior to December 1989, this fish was very common throughout the mangrove ecotone. The Christmas freeze of 1989 annihilated the species; no individuals were collected for more than a year and the species as a whole was uncommon in our collections until late in 1991. Since that time, this species has continued to increase in both number and biomass and, where abundant, the increase in the cichlid population has been coincident to a decline in native species. Furthermore, the range of the Mayan cichlid continued to expand. The species was never collected at our BL site, although it was captured incidentally at nearby locations. In June 1995, the last scheduled sample to be collected at BL contained breeding adults and juveniles of this species. BL will continue to be sampled indefinitely so that any changes in community structure will be documented.

Funding for periodic collections of fishes was terminated as of June 1995. At this time, we have no intention of actively pursuing further funding for continued periodic samples. Recent discussions with ENP raised the potential for including at least some of the sites in a biological monitoring program to assess iterative processes proposed by the COE and the SFWMD concerning modified water deliveries to Taylor Slough. If funding is made available, the collection of samples may be restarted in the future. At present, our research goals are to pursue funding to conduct specific experiments designed to support our findings to date. These experiments will be along two avenues: 1. To more closely examine the relationship of salinity (and possibly nutrient delivery) to primary and secondary productivity, and 2. To elucidate the impact of the exotic Mayan Cichlid on the ecosystem.

Fish and Shrimp Populations on Seagrass -Covered Mud Banks in Florida Bay: 1984-'86 versus 1994-'95

R.E. Matheson, Jr. , D.K. Camp, K.A. Bjorgo, Florida Department of Environmental Protection, Florida Marine Research Institute.

The faunal community of seagrass beds in Florida Bay includes, among other elements, large numbers of fish and decapod crustaceans. These animals include juveniles of some species (transients) as well as all or most life­history stages of other species (residents). Populations of transients often have pelagic larval stages whose recruitment to the Bay can be greatly affected by oceanographic processes operating outside of the Bay, and these animals are also often the subject of extensive fisheries (e.g., pink shrimp, Penaeus duorarum; gray snapper, Lutjanus griseus). Residents, on the other hand, may be better

http://www.aoml.noaa.gov/flbay/fish95.html (8 of 14)9/10/2007 2:32:35 PM Fisheries-1995 indicators of overall ecosystem health because they are less affected by processes operating outside of the system and because they are not harvested by man. They are, however, an important element in the diet of predatory fish and birds that utilize Florida Bay as a feeding ground. The seagrass fauna (both resident and transient) could be greatly affected by seagrass die­off and is also vulnerable to the effects of algal blooms and changes in freshwater input. From 1984 through 1986 (prior to the recent seagrass die­off), Powell et al. (1987) used 1­m2 throw traps to collect quantitative data on the forage fish and decapod community. Throw traps of this type are biased toward the resident portion of the fauna. During 1994 and 1995 we repeated a portion of the work of Powell et al. (1987) with the goals of documenting changes occurring in seagrass­associated fauna since the recent seagrass die­off and providing baseline data for evaluating the effects of planned future ecosystem changes on this fauna. This work addresses Questions 1 and 2 in the "Living Resources" section of the Science Plan for Florida Bay. It is most pertinent to Task i ("Develop baywide faunal monitoring program...Compare results with past studies) of Question 1 and Tasks i and ii ("Collect unbiased information on...indicator species" and "Focus on habitat­based research...pre­ and post­die­off seagrass and mangrove faunal community composition must be quantified") of Question 2. In this presentation we will compare physical, seagrass, fish, and shrimp data collected in these two studies.

We conducted our sampling with one of the throw traps used by Powell et al. This trap is a box with each side 1­m wide by 45­cm deep and without top or bottom. The effective depth of the trap was extended by a floating net of 3­mm mesh attached to the top of the box at one end. To collect a sample, we randomly threw the trap over a seagrass bed, and forced the trap frame into the bottom in order to isolate 1 m2 of seagrass. We then removed animals by using an internal seine. Each trap was seined a minimum of ten times, and seining was continued until three successive passes produced no organisms other than, as in the previous study, mud and hermit crabs. We also collected two 15.3 cm core samples with each throw­trap in order to characterize the seagrass bed in terms of seagrass species, shoot density, leaf surface area, and mean blade length and width. With the exception of two sites in March 1994, six throw­trap samples were collected from each site on each sampling date. To date we have collected samples in March and September of 1994 and June of 1995. This corresponds to the dry season and the early and late wet seasons of the previous study, but we will refer to them by their calendar seasons and call them our winter, autumn, and summer samples, respectively. Physical data and fish data that we present here include all three sampling periods for both studies, while shrimp and seagrass data include only the winter and autumn periods.

Sampling in both studies was conducted on banks representing five different vegetational subenvironments of the bay as defined by Zieman et al. (1989): the Atlantic near the Buchanan Keys (Buchanan), the East Central near Cowpens Key on Cross Bank (Cross), the Northeast near Eagle Key (Eagle), the Interior near Coon Key (Coon) and between Roscoe and Dump Keys (Dump), and the Gulf near Oyster Keys (Oyster). Buchanan is characterized by a moderate tidal range and good exchange with the Atlantic Ocean. Cross has a small tidal range and is isolated by other banks from either freshwater or marine exchange. Eagle has a small tidal range, but is near the Taylor River emptying into Little Madeira Bay and is, therefore, susceptible to freshwater input from the mainland. Coon and Dump both have a small tidal range and are isolated from both freshwater and marine exchange. Oyster has a large tidal range and is open to the Gulf of Mexico. The previous study employed a stratified sampling design

http://www.aoml.noaa.gov/flbay/fish95.html (9 of 14)9/10/2007 2:32:35 PM Fisheries-1995 with the strata being transects along the top and either side (ca. 50 cm deeper than the top) of a given seagrass­covered mud bank. Our comparisons here include only the leeward transects from the 1984­'86 study.

Temperature and salinity varied somewhat between the two studies, but the differences were not pronounced and were probably of little consequence to the fauna. At three of the six sites we sampled under warmer conditions than were recorded in 1984­'86. At Buchanan and Dump this included both our summer and autumn samples and at Coon this included a portion of our autumn sampling. The overall temperature range for all sites combined in 1994­'95 did not, however, exceed that in 1984­'86. Salinity differences between the two studies are also rather unremarkable. In both studies the lowest salinities were recorded at Eagle. At the two interior sites, Coon and Dump, slightly lower salinities were recorded in winter and summer of 1994­'95, and at Coon slightly higher salinities were recorded in autumn of 1994­'95. Again, the overall range in 1994­'95 did not exceed that in the previous study.

In contrast to the physical data, a marked change occurred in seagrass density over the ten­year period at one of the six sites: there was a large decline in seagrass density at Dump. Otherwise, increases in seagrass density were recorded for the beds at Eagle and Coon, but density at these sites was relatively low in both studies. Seagrass density at Buchanan and Cross was relatively high in both studies, and seagrass density at Oyster was somewhat intermediate between the low values at Eagle and Coon and the high values at Buchanan and Cross.

Among the fish, most sites were numerically dominated in both studies by two species that we term "canopy residents", the rainwater killifish (Lucania parva) and the goldspotted killifish (Floridichthys carpio), and two species that we term "benthic residents", the gulf toadfish (Opsanus beta) and the code goby (Gobiosoma robustum). Canopy residents may live near the substrate but are relatively motile and are often found up in the water column; they may, therefore, be quite reliant upon seagrass for cover. Benthic residents live on or in the substrate, are less motile, and may depend less on seagrass cover. Fish species richness in both the 1984­'86 and 1994­'95 studies was highest at the two stations with free exchange with marine waters, Buchanan (25 and 16 species, respectively, in the two studies) and Oyster (20 and 16 species), and lowest at the two interior sites, Coon (6 and 9 species) and Dump (9 and 10 species).

Among the decapods, the bryozoan shrimp, Thor floridanus, numerically dominated all sites in 1994­'95 and all but Oyster in 1984­'86. Several other grass shrimp in the genera Periclimenes and Hippolyte were prominent at most sites as were alpheids (genus Alpheus). Pink shrimp, Penaeus duorarum, were prominent at Oyster in both studies and at Buchanan and Coon in 1994­'95. As with the fish, the shrimp faunas at Buchanan (12 and 9 species) and Oyster (12 and 11 species) were the most speciose, with richness being much lower at the other sites (only two species were collected at Dump in 1984­'86).

Total fish density in both studies was highest at Dump and lowest at Eagle despite a significant decrease at Dump and increases at both Eagle and Oyster over the ten­year period. Median numbers ranged from 28 and 22.5 fish per m2 (for 1984­'86 and 1994­'95, respectively) at Dump to 3 and 7 fish per m2 at

http://www.aoml.noaa.gov/flbay/fish95.html (10 of 14)9/10/2007 2:32:35 PM Fisheries-1995 Eagle. Density of benthic resident fishes increased significantly over the ten­year period at both Dump and Oyster but did not change elsewhere. Density of canopy residents was more variable between the two studies, with significant differences at five of the six sites. These differences included declines and Dump, Buchanan, and Cross and increases at Eagle and Oyster. An overall comparison of fish community composition at the six sites revealed that the most marked change was in the increased percentage of the fish community comprised by benthic versus canopy species at Dump. At the species level, this change at Dump was due to a significant density decrease in one canopy resident, rainwater killifish, and significant increases in two benthic residents, code and clown gobies.

We suspected that the increased densities of total fish, benthic residents, and canopy residents at Oyster might be due to a different mix of Halodule­versus Thalassia­dominated samples in the two studies (this site has the most heterogeneous seagrass bed of any of our sites). A closer investigation of this phenomenon, however, revealed that Halodule­dominated samples collected in 1984­'86 produced significantly fewer fish than did Halodule­dominated samples collected in 1994­'95. This situation warrants further investigation.

By dividing the shrimp community into three categories (small carideans [with a variety of lifestyles], alpheids [benthic], and penaeids [generally inactive by day]) we found and increased importance (in terms of percent faunal composition) of benthic species at Dump, Coon and Oyster. Overall densities of the numerically dominant shrimp, Thor floridanus, parallel those of fish, with densities at Eagle and Coon being lower and those at Dump, Cross, and Buchanan being higher. In this case, however, the density at Oyster was also low. Significant changes over the ten­year period occurred at Coon and Dump (decreases) and Eagle (increase), but, again, the most dramatic difference was at Dump, with the median value dropping from 978 to 52 T. floridanus per m2. The benthic alpheids increased at Coon, Dump, and Oyster and decreased at Cross. The dramatic increase at Dump is evidenced by a change in the median density value from 0 to 11 alpheids per m2.

In summary, the most dramatic changes among these six banks occurred at the site near the Dump Keys. At most sites salinity, temperature, and benthic fish densities changed little over the ten­year period. Other parameters were more variable, but the greatest changes were at Dump. Species richness of shrimp and fish in both studies was greatest at the sites with the most marine influence and least at the sites most isolated from either marine or freshwater influence. Inter­site fish density patterns were also similar between the two studies, with the low­circulation, freshwater­influenced Eagle site and the low­ circulation Coon site producing the fewest fish. Densities of seagrass, total fish, canopy fish, and Thor floridanus all declined significantly at Dump. Benthic fish and alpheid shrimp densities, on the other hand, increased significantly.

At the species level the change in the fish community at Dump was due to a significant decrease in the abundance of rainwater killifish and significant increases in the abundance of code and clown gobies. What does this change translate into in terms of forage fish on this bank? If we take the statistical liberty of averaging our density data over the 922,860 m2 area of bank between the southernmost Dump Key and Roscoe Key, and also turn our numbers into biomass based on the average weight for each species at Dump, we estimate that, on any given day, this bank community contained 1,590 kg less rainwater

http://www.aoml.noaa.gov/flbay/fish95.html (11 of 14)9/10/2007 2:32:35 PM Fisheries-1995 killifish biomass and 822 kg more code and clown goby biomass during 1994­'95 than during 1984­'86. For the piscivore this means approximately half the forage biomass concentrated in these three numerically dominant species. The ultimate effect of this change, however, may also be influenced by differences in predator efficiency in dense versus sparse seagrass and in capturing canopy versus benthic prey.

In the immediate future we plan to continue sampling at some or all of our sites in order to obtain a database more comparable to the 1984­'86 database, initiate sampling in other areas of interest (based on perceived changes occurring in seagrass beds at these locations, among other factors), and begin (with the collaboration of other researchers) an evaluation of the health of resident animals at different locations in the Bay (e.g., parasitological and histological studies) and conduct further analysis of our decadel comparison.

Status of Gamefish Harvest Monitoring in Florida Bay, Everglades National Park

Thomas W. Schmidt, Everglades National Park, South Florida Natural Resources Center, 40001 State Road 9336, Homestead, Florida 33034-6733.

Fishing activity and harvest of sportfish from Everglades National Park have been monitored nearly continuously since 1958. It is one of the oldest, ongoing marine creel census surveys in the U.S. This monitoring program was orginally initiated because of concern over greatly increased fishing pressure resulting from the construction of a highway, marina facilities and access canal to in 1958. The first ten years of the program (1958-69) were conducted through contract with the University of Miami and were directed at evaluating only the sport fishery at Flamingo. Over 75 species of fish have been reported within the recreational catches; however , five species (gray snapper, spotted seatrout, red drum, sheepshead, and black drum) have comprised over 86% of the catch since 1958. In 1965, a permitting system was instituted for commercial (hook and line, netting, trapping and professional guides) fishermen operating in the park. Harvest of three top sportfish; gray snapper, seatrout, and red drum approached maximum sustained yield (MSY in numbers) between 1974 and 1986 when commercial fishing was permitted. Until 1972, these catch data consisted of monthly total harvest, by species, for each fisherman. The harvest reports were voluntary and did not include any measure of fishing effort or specific areas of fishing harvest so it was impossible to monitor populations by ecosystems or management unit, or to evaluate the degreee to which fishermen complied with the reporting requirements of there permits. In 1972, the NPS expanded the harvest monitoring program to include daily trip ticket reports from the commercial permit holders, fishing area classifications, effort data, random field checks by patrol rangers for compliance, and developed censusing techniques to evaluate total parkwide sport fishing and commercial effort. In 1978 a detailed account of the park's fishery database was completed in response to sport fishermen and professional guide complaints of declining stocks. An overall decrease in fish stocks was noted during the mid-1970's, these declines are

http://www.aoml.noaa.gov/flbay/fish95.html (12 of 14)9/10/2007 2:32:35 PM Fisheries-1995 believed to have been the result of low rainfall and reduced estuary runoff resulting in increased natural mortality and reduced recruitment rather than harvest. In 1980, new regulations were established to create aggregate bag limits for both commercial and sport fishermen, mandatory reporting as a condition of a permit, and to abolish all commercial fishing (except for guides) after 1985.

This report presents an analysis of catch/harvest data from Florida Bay ( Areas 1-5) to evaluate current trends in abundance for the top four gamefish species, (red drum, spotted seatrout, gray snapper and snook), based on recreational guide and non-guided catch and harvest per unit of effort data (CPUE, HPUE). These data include: (1) recreational winter quarter ramp data from Flamingo 1980-90 and 1995, (2) annual guide data within the park (1980-1989, and 1994), and (3) 1994 guide data, stratified by fishing area and projected on GIS maps. Monthly guide reports consist of daily trip entries indicating amount of effort (hours fished), resultant catch, number harvested and area fished for each day. All of the recreational non-guided fishermen catch data for Florida Bay has come from weekend day interviews conducted at the Flamingo boat ramps. Monthly guide reports and interview sheet summaries provide estimates of catch and harvest (fish landed) per unit-effort for successful fishermen (those fishermen who caught spotted seatrout, red drum, gray snapper, snook).

For seatrout, during 1980-90 and 1995, a similar general pattern was seen for the average number of spotted seatrout harvested per successful boat and per hour of fishing out of Flamingo, as that shown by guide catch/harvest per hour data for 1980-90, and 1994. The lack of increase in harvest per boat and per hour fished in 1994, may be due to regulations imposed on the fishery in 1989 by the state of Florida and adopted by the park which raised the legal size limit from 12" to 14", For 1995 quarterly data, seatrout reached new highs in numbers released and may reflect a good stock recruitment of small juvenile seatrout. Lower catches were reported in southern Florida Bay (Area 2). During the most recent winter quarterly periods analyzed, 1990 and 1995, snook catch rates abruptly increased over the 1987-89 period and reflect a good stock recruitment of small juvenile snook . The large increase in catch/harvest rate from 1982-86 occurred despite size and bag limits and a five month closure on the fishery. Because of length-limit restrictions and closed seasons on snook and possible changes in fishing behavior, an unknown number of fishermen are releasing their catch to support recent promotions in catch-and- release fishing. Snook catches were highest in the 10,000 Islands and lowest in southern Florida Bay.

For red drum, during 1989-90 and 1995, the average winter harvest per successful boat at Flamingo has followed a pattern similar to that of winter average harvest rate per man-hour. The lack of increase in harvest per boat and per man-hour is probably due to the 1989 bag limits of 1 fish per person following almost two full years of prohibited harvest (1987-88). Increased size limits (12'' to 18") and a closed season imposed on the fishery in September 1985 probably accounted for the large declines in average harvest per boat and per man-hour fishing in 1986, however, the sharp declines in harvest rates during 1985 suggest the possibility of overharvest or poor recruitment. The increase in 1995 average winter catch per boat and per man-hour fishing may be a result of the decline in harvest/catch rates from 1985 to 1990, allowing offshore stocks to rebuild and recruitment to increase in Florida Bay as observed in winter 1995. Guide harvest rates of red drum from 1980 to 1984 have followed catch rates being highest in 1983 and lowest in 1982. The large decline in harvest from 1985 through 1987 is probably due to increased minimum size limits. Slightly higher catch rates were found in areas 2 and 5, the outer reaches

http://www.aoml.noaa.gov/flbay/fish95.html (13 of 14)9/10/2007 2:32:35 PM Fisheries-1995 of the estuary, than in areas 1, 3, and 4, the more inland portions of the Bay, and is probably due to the fact that red drum recruit to the park's fishery from offshore waters. During the 1990's, the average number of gray snapper harvested per successful trip and per hour of fishing out of Flamingo has dropped as low or lower than anytime during the previous record and the trend may continue downward. For the guides, there was little annual variation in CPUE/HPUE until 1990 when the HPUE dropped lower than anytime during the previous record. One factor that partially explains the lower harvest per boat and per hour fishing may largely be due to the regulations imposed on the fishery in 1988 when the legal minimum size was increased from 6 to 8 inches, and in Feb.1990, which established a minimum legal length of 10" and a bag limit of 5 fish per person. During 1989-90 and 1995, the increase in catch but not harvest may reflect a good stock recruitment of small juvenile fish which are being released because of size regulations. In 1994, the highest catch rates of gray snapper for Florida Bay were found in Area 2. Recent studies of larval and juvenile fish within the park suggest that coral reefs off the middle and lower Florida Keys probably supply much of the recruitment to the park population. Spawning occurs on the reefs and the larva drift to the estuaries via tidal flow. Therefore, management of the park's gray snapper population must consider harvest occurring outside the park particularly in respect to recruitment. Although recent bag and size limits and seasonal closures have reduced harvest, catch rates for seatrout, snook, and red drum have increased in the 1990's.

Last updated: 04/23/98 by: Monika Gurnée [email protected]

http://www.aoml.noaa.gov/flbay/fish95.html (14 of 14)9/10/2007 2:32:35 PM http://www.aoml.noaa.gov/flbay/hydro95.html

Hydrology

1995 Abstracts

Submarine Groundwater Discharge

Jeffrey Chanton, William Burnett, Jaye Young, Glynnis Bugna, Department of Oceanography, Florida State University, Tallahassee, Florida 32306-3048, 904-644-6700

The purpose of our study is to evaluate the significance of groundwater discharge into Florida Bay. We have attempted to locate areas in the bay where groundwater seepage is more pronounced by reconnaissance surveys of the concentrations of radon and methane in the bay waters. These trace gases are thought to be good natural indicators of seepage of groundwaters into standing bodies of water (see below and Young et al., 1995). We have observed a wide range in 222Rn and CH4 concentrations in the bay waters with systematically higher values in the "back-key" basins investigated relative to the northern bay sites and especially the mid-bay stations (Figure 1). Using this information as a guide, we returned to Florida Bay to make direct measurements of groundwater seepage using an instrument design modified from Lee (1977). The "seepage meter" is basically a chamber implanted in the sediments which has an open port where a plastic bag can be positioned to collect seepage over measured time intervals. We used 4-liter plastic bag "collectors" which were prefilled with 1000 mL of bay water to prevent short-term artifacts (Shaw and Prepas, 1989) and to allow for measurements of negative seepage, i.e., recharge into the underground aquifer. The lower reliable measurement limit for seepage meters depends upon the length of deployment and the conditions under which the sampling occurs-based on our experience using these meters, we normally expect a lower useful limit of 3-5 mL/ m2.min. Over two hundred seepage measurements were conducted on sampling trips in February and July, 1995. Our seepage sampling sites are shown (Fig. 2), for three geographic groupings: (1) open bay; (2) northern Florida Bay; and (3) back-key areas. Seepage can be highly variable, both on a temporal and spatial basis, even within small areas. Often seepage decreases as one moves away from shore. Many of our transects were arranged perpendicular to shore and so high spatial variability should be expected. Standard deviations were often of the same magnitude as the means. Numbers of replicates ranged from 4 to 8 meters.

The "mid bay" sites included a circular seagrass bed off Buchanan Keys, two transects along the western and eastern edge of Rabbit Key Basin, and one in Whipray Basin. The seepage rates from Rabbit Key Basin and Whipray Basin were low; daily means of 9, 5 and 6 ml m-2 min-1 were obtained. The results from the circular bed near Buchanan Key were somewhat greater and means of 20, 7 and 18 mL/m2. min. were obtained. Two measurements in the western transect at Rabbit Key showed significant seepage at about 30 and 40 mL/m2.min. These single measurements, however, were taken in shallow water during a period of high winds and should thus be viewed cautiously. The circular seagrass bed off

http://www.aoml.noaa.gov/flbay/hydro95.html (1 of 24)9/10/2007 2:32:37 PM http://www.aoml.noaa.gov/flbay/hydro95.html Buchanan Keys did show some relatively high seepage values (up to about 40 mL/m2.min) which were verified on subsequent visits. Pairs of measurements made at this site showed reasonably good precision for measurements made within a time span of a few hours.

In northern Florida Bay (Long Sound, Snipe Point, and two sites in Madeira Bay), the seepage rates were generally low. Although a large variation existed between the two days when measurements were made, the seepage at Snipe Point appeared higher (daily means of 24 and 4 mL/m2.min. Measurements were only made on a single day at both Madeira Bay and Madeira Beach.

Some of the most interesting measurements were taken in the "back-key" areas, i.e., those areas just on the Florida Bay side of the Keys. This area generally had greater tracer concentrations in the December 1994 survey. The areas where measurements were conducted included the Key Largo Ranger Station, Tavernier Basin, Hammer Point, and Little Buttonwood Sound. Measurements off the Ranger Station were low and variable, even when made within a short time frame. Seepage in Little Buttonwood Sound, on the other hand, was moderate (daily means of 12 and 14 mL/m2.min, highest value = 56 mL/m2.min) although there was still considerable spatial variability between the meters which were all placed within a relatively small area (approximately 50 x 100 meters). The measurements made at Tavernier Basin were the highest and spatially most consistent we have measured to date in Florida Bay. The mean of 6 meters placed in a seagrass bed within an area of about 500 m2 was 68±5 mL/m2.min. This area had also produced one of the highest concentrations of radon and methane in our December measurements (see Figure 1). Six seepage meters installed in a 500-m line at Hammer Point, another site of high tracer concentrations based on our initial sampling trip, were measured repeatedly over a several day period. These repetitive measurements turned out to be a productive strategy as a clear pattern developed which showed a relationship to the tidal cycle on the Atlantic side of the Keys (Fig. 3). This pattern, which shows a trend towards higher seepage on the Florida Bay side of the Keys when the Atlantic tide is high, and lower (negative) seepage when the Atlantic level is low illustrates that tidal forcing may be of paramount importance in terms of controlling seepage into (and out of) Florida Bay (see also Halley et al., 1994).

Analysis of the monitor well waters (of Dr. Gene Shinn) showed that the underground waters were fairly uniform in 222Rn while the CH4 concentrations were more variable. Out of 19 samples, all 222Rn values except 1 were in the range of 300-650 dpm/L and most CH4 values were in the range of 100- 1000 nM with 3 lower concentrations and one sample (KL5) that was spectacularly higher at about 15,000 nM. Note that these concentrations are significantly enriched relative to concentrations in surface waters, suggesting that the tracers may be good indicators of groundwater intrusion. Interestingly, the Key Largo (KL1-KL5) transect showed a general trend of increasing radon in an offshore direction (perhaps indicating an increase associated with increased residence time) and a general decrease in methane offshore (with the exception of the extremely high value at KL5). Sulfide concentrations (measured by Dr. Paul Carlson) showed a similar pattern as CH4 in these wells.

Halley, R.B., Vaciler, H.L., Shinn, A. and Haines, J.W. Marine Geohydrology: Dynamics of subsurface seawater around Key Largo. 2nd Coastal Wetalnd Ecology and Management Symposium, Key Largo, 1994.

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Lee, D.R., 1977. A device for measuring seepage flux in lakes and estuaries. L&O, 22, 140-147.

Shaw, R.D. and E.E. Prepas, 1989. Anomalous, short-term influx of water into seepage meters. L&O, 34, 1343-1351.

Young, J., Bugna, G., Burnett, W. and Chanton, 1995. J. Application of Radon and Methane for assessment of groundwater discharge in coastal and offshore waters. submitted to Limnology and Oceanography.

Geophysical Mapping of Fresh/Saltwater Interface

David V. Fitterman, U.S. Geological Survey.

Introduction

Water quality in coastal areas of South Florida such as Everglades National Park (ENP) and the discharge of fresh water into Florida Bay are closely tied to water use and water management policies. Determination and monitoring of water quality is essential to restoration of the South Florida ecosystem (SFE). Increased domestic water use, drainage of land to allow farming, increased farming and subsequent nutrient loading of runoff, and changes in water management practices over the years have had a profound effect on the SFE. Monitoring of these effects is made difficult by the inaccessibility of much of this area. Airborne geophysical methods provide a means of rapidly and economically monitoring large areas where access is difficult.

Project Objective and Scope

This project addresses the question of determining the location of the fresh-water/salt-water interface (FWSWI) in the coastal regions of southern Dade and Monroe Counties, synoptic monitoring of changes in water quality associated with changes in water management practices, and looking for geophysical evidence of subsurface discharges of fresh water to Florida Bay.

This project covers a 1036-square-kilometer region of the Everglades located in Everglades National Park and surrounding areas. The study area is bounded on the east by U.S. Highway 1, on the south by Florida Bay and Whitewater Sound, and on the far west by the mouths of the Harney River and Shark River Slough. From these boundaries the study area extends inland from 14 to 22 km.

Summary of Methods

http://www.aoml.noaa.gov/flbay/hydro95.html (3 of 24)9/10/2007 2:32:37 PM http://www.aoml.noaa.gov/flbay/hydro95.html This project relies upon the fact that changes in water salinity produce changes in specific conductance (SC) or water resistivity. As pore fluid resistivity strongly influences the bulk resistivity of geologic materials, geophysical methods which measure rock resistivity can be used to obtain information on ground water quality.

Airborne electromagnetic geophysical surveys are used to collect resistivity data. The interpreted data provide information on geologic and hydrologic conditions including locations of geologic boundaries and spatial changes in water quality, which are of use to ground-water modelers. Interpretation relies heavily upon the use of borehole geophysical logs, namely induction logs from monitoring wells and water quality data. Surface geophysical measurements are used to refine the interpretation. Resistivity maps and their interpretations will be of use to agencies managing water levels in South Florida and assessing their impact on the SFE.

The primary tool used in this study is helicopter electromagnetic (HEM) surveys. A large (9-m-long) cigar-shaped instrument package called a "bird" is slung 30 m below a helicopter. Electrical current flowing in transmitter coils in the bird induces current in the ground. The intensity of the induced currents increases as the ground conductivity increases. The magnetic fields generated by the induced currents are recorded by receiver coils in the bird. The transmitter coils are excited at five frequencies to obtain different depths on investigation. Flying with the bird 30 m above the ground, measurements are made every 0.1 second along flight lines. Flight lines are nominally spaced 400 m apart. Analysis of these data produces apparent resistivity maps. Using multi-frequency data sets, the data are inverted to obtain resistivity-depth information along flight lines. Resistivity-depth results are used to generate cross sections and interpreted resistivity maps, such as depth to geologic or hydrologic interfaces.

Water quality measurements from monitoring wells will be used along with borehole resistivity logs to establish the relationship between water quality and formation resistivity. Laboratory measurements of cores from wells in the area will be used to refine the water-quality-formation-resistivity correlation. This correlation is needed to convert interpreted resistivity maps into water quality maps.

Summary of Results to Date

HEM apparent resistivity data collected in December 1994 show a resistivity transition becoming more conductive in the direction of Florida Bay. This feature is interpreted to be the fresh-water/salt-water interface (FWSWI). The transition is narrowest where water from Taylor Slough forces the transition seaward and becomes more dispersed to the east of Taylor Slough and between Taylor Slough and Shark River Slough. These sloughs show up as resistive features due to the fresh ground-water flows associated with them. There are several features on the maps which are attributed to the effect of man- made structures on ground-water flow. These include: a conductive feature along the old Ingraham Highway caused by the road bed blocking fresh-water flow southward which would wash away more saline water, 2) discontinuities in the resistivity values across the Flamingo road suggesting that the road bed inhibits water flow, and 3) resistive features near the S18C control structure on the C-111 canal suggesting that water impounded by the control structure flows into the surrounding aquifer.

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In the region west of the Flamingo road toward the area of Tarpon Bay, the resistivity maps are dominated by the influence of tidal flow of saline to brackish water in the streams draining west and southwestward to the coast. The resulting resistivity transition attributed to the FWSWI is just inland of the upper reaches of most of these drainages. Coastward of Tarpon Bay, the area is uniformly conductive except for a small resistive feature thought to be associated with a fresh-water lens sitting under a small topographic high. The region is marked by vegetation changes indicative of higher ground and less saline ground water than the surrounding terrain which is covered by mangrove.

Interpretation of the FWSWI in the airborne resistivity data is confirmed by borehole geophysical logs and water quality data. We have established a correlation between formation resistivity and water specific conductance in the eastern part of the study area. Wells drilled farther to the west will provide information indicating if this correlation is valid over a wider region.

Helicopter electromagnetic (HEM) surveys were flown in April 1994 and December 1994 at the end of the dry and wet seasons respectively providing information at extremes of the hydrologic cycle. Comparison of the dry season (April 1994) and wet season (December 1994) HEM surveys shows that there is an increase in apparent resistivity of nearly a factor of 2 along the main portion of the FWSWI. This is attributed to increased fresh-water flow in the surface and near-surface portions of the aquifer. There is a very pronounced increase in resistivity in Long Sound and Madeira Bay. We interpret this as being caused by these water bodies becoming fresh due to increased fresh-water discharges from the Everglades during the wet season. Conductivity monitoring in Long Sound by the National Park Service confirms this hypothesis as well as conductivity surveys conducted in Florida Bay by USGS. The resistivity changes are very encouraging as they suggest that HEM surveys can be used to monitor the long term effect of changes of water flows in the Everglades. Repeat HEM surveys are planned over the next four years to monitor temporal resistivity changes.

Borehole geophysical data including induction logs and water specific conductivity measurements were collected starting in September 1994. To date a total of 16 wells have been logged. Additional wells are planned in and near ENP. These wells will be logged on a regular basis to monitor changes in resistivity associated with changes in surface and ground-water flows. Further analysis is needed to determine required frequency of repeat logging.

Time-domain electromagnetic soundings were collected during August 1995 at 35 locations in Everglades National Park. These soundings give very detailed information about the resistivity-depth structure from the surface to a depth of about 80 m. These data are being used to calibrate the HEM survey results.

The Importance of Taylor Slough Hydrology on Salinities in Florida Bay

Robert A. Johnson, Robert J. Fennema, Everglades National Park, South Florida Natural Resources

http://www.aoml.noaa.gov/flbay/hydro95.html (5 of 24)9/10/2007 2:32:37 PM http://www.aoml.noaa.gov/flbay/hydro95.html Center, 40001 State Road 9336, Homestead, Florida 33034-6733.

Taylor Slough is a freshwater wetland system which encompasses more than 158 square miles, and extends some 20 miles from its upstream end north of the Frog Pond to the coastal mangrove fringe along Florida Bay. The headwaters of the slough originate in the Rocky Glades, a transitional wetland which separates Shark Slough and Taylor Slough. The slough has historically been an important source of freshwater to the central portion of Florida Bay. Prior to the 1960's, wet season water levels in the Rocky Glades and Taylor Slough headwaters were 1.5 to 2.5 feet higher than today (Johnson and Fennema, 1989). These higher water levels kept the northern Taylor Slough marshes inundated for 2 to 3 months each year, and established a hydraulic gradient that sustained surface water and groundwater flows into Florida Bay. The higher water levels also retained much of the local wet season rainfall in the wetlands and underlying aquifer, which allowed freshwater to be releasedmore gradually, tempering salinity fluctuations in the nearshore areas of Florida Bay.

Beginning in the late 1960's, construction of the Central and Southern Florida (C&SF) Project features in southwestern Dade County led to the drainage and diversion of flows away from the slough, and into the lower C-111 basin and the east coast canals to Biscayne Bay. These changes are thought to be an important contributor to the hypersaline conditions in the nearshore embayments of central and northeastern Florida Bay. Everglades National Park has been working with the Army Corps of Engineers and the South Florida Water Management District for the last ten years on modifications to the C&SF Project features in the Taylor Slough and C-111 basin to reduce ENP drainage losses, and reestablish more natural surface water inflows through Taylor Slough and into Florida Bay. A key to these efforts is the need to quantify the relationships between upstream hydrologic conditions and salinities in the downstream estuaries, in order to establish restoration guidelines for this redesign effort. Our current project is a preliminary effort to link the long-term changes in upstream water levels to fluctuations in nearshore salinities using simple statistical models, and the results of numerical hydrologic models developed for the south Florida region.

A number of scientists have developed regression models that attempt to link salinities in the nearshore areas of Florida Bay to water levels in the uplands (Tabb 1967, Sculley 1986, Bjork and Powell 1994, and Cosby 1994). These efforts use the results of univariate and multivariate regression models developed by Dr. B.J. Cosby to simulate daily and monthly salinity variations in Trout Cove, Long Sound, Joe Bay, and Little Madeira Bay, based on water levels at long-term monitoring wells in and adjacent to the Park. These statistical models were initially developed to use the 40 plus years of historical water level data in the uplands to reconstruct salinity patterns in the bay. All of these studies have shown that upland water levels are statistically linked to salinity variations in the nearshore areas of the bay, and that historical reductions in upland water levels have contributed to the hypersaline conditions in the bay. Several of these statistical models were next combined with the results of a series of regional hydrologic modeling runs using the South Florida Water Management Model, to test the hypotheses that the hydrology of Taylor Slough is of specific importance to salinities in the nearshore areas of Florida Bay, and that increasing water levels in the upper portion of the slough is an appropriate way of restoring more natural variations in downstream salinities.

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Model runs with increased upland water levels in the Rocky Glades and upper Taylor Slough basins (simulating the effects of pre-drainage conditions) were found to temper the observed short term and seasonal salinity variations, reduce the occurrence and duration of hypersaline periods, and prolong the beneficial effects of wet season runoff well into the following dry season. These changes were most pronounced at the salinity monitoring sites in the nearshore areas of central Florida Bay (Madeira Bay), and less pronounced for the sites in northeastern (Florida Bay). This suggests that water management impacts have had there greatest effect on reducing inflows into the bay via Taylor Slough, and that current efforts to divert excess runoff from the Eastern Panhandle basin into Taylor Slough will likely lead to salinity problems in the nearshore embayments downstream of the C-111 canal system. For this reason, the restoration of more natural freshwater inflows into Florida Bay via Taylor Slough will most likely require redirecting the historical wet season runoff that is currently lost to Biscayne Bay, or provisions to provide supplemental inflows from the upstream regional water management system.

Reconstruction and Simulation of Episodic Meteorological Events and Local Weather Regimes Which Affect the South Florida Ecosystem

Craig Mattocks, NOAA - University of Miami Cooperative Institute for Marine and Atmospheric Studies; Mark Powell, Sam Houston, NOAA - AOML Hurricane Research Division, Miami Fl.; Mark DeMaria, NOM - NWS National Hurricane Center, Miami Fl.

Introduction

The primary objective of this research project is to reconstruct episodic/catastrophic meteorological events and local weather regimes which critically affect the South Florida ecosystem. Gridded wind, precipitation, and temperature fields will be generated from real case analyses, numerical model simulations, and idealized scenarios described by canonical systems of analytical equations to produce a catalog of datasets. Research scientists will be able to quickly retrieve data from this event/regime archive for use in circulation model simulations/predictions, hydrological modeling, natural systems restoration, and biological impact studies.

Episodic Wind Field Reconstruction

Attendees of the South Florida Atmospheric Modeling Workshop (NOON, Nov.1994) expressed the need for a catalog of meteorological events/regimes which critically affect the South Florida ecosystem. Gridded datasets from this archive could be accessed for circulation/ecological model simulations, hydrological modeling, natural systems restoration, and biological impact studies. During the next several months, events to be studied include Hurricane Andrew (August 1992), the "Storm of the Century" (March 1993), Tropical Storm Gordon (November 1994) and Hurricane Donna (1960). Next year, additional reconstructions will include the Florida Keys Hurricane of 1935 and other historical catastrophic storms. Quality control procedures, spatial/temporal averaging techniques, planetary

http://www.aoml.noaa.gov/flbay/hydro95.html (7 of 24)9/10/2007 2:32:37 PM http://www.aoml.noaa.gov/flbay/hydro95.html boundary layer adjustment algorithms to account for land/water exposure, hurricane wind field models, and an objective analysis technique which minimizes the error between the analyzed field and the input observations have been developed by HRD scientists (Powell et al,1995) for such applications. "Snapshots" of the surface wind streamline and isotach fields will be generated for a regular (latitude, longitude) domain centered on Florida Bay at 6-12 hour intervals. These images and gridded surface wind datasets will be archived on a World Wide Web site for access by other Florida Bay researchers. A format will be chosen which will allow these fields to be imported by geographical information systems (GIS) so that they can be overlayed/compared with other geo-referenced datasets such as mangroves, reefs and turbidity plumes.

Mesoscale Atmospheric Modeling

A major component of this dataset construction effort is the use the Advanced Regional Prediction System (ARPS) mesoscale atmospheric numerical weather prediction model which can simulate/predict surface winds, rainfall and thermodynamic fields relevant to Florida Bay at high-resolution. These fields can be used as boundary conditions/forcing for bay and ocean circulation models. The atmospheric model can also be used to study the effect of specific processes on the freshwater input to Florida Bay, such as evaporation/precipitation under different weather regimes, as well as the transport/rainout of toxic atmospheric substances in the South Florida ecosystem. The model was initialized with a homogeneous base state from the 12 UTC 25 August 1975 Miami sounding, which corresponds to the FACE case described by Cunning and De Maria (1986) and Cunning et at., (1986) . ARPS was configured to be DRY (safe, solid run), with a horizontal grid mesh of 9 km, and 42 vertical levels using a tangential vertical grid stretching (50 meter vertical resolution in lowest 500 meters, slowly increasing to 500 meters at 700 my, then reaching a man stretched spacing of 1 km in the stratosphere). A clay- loam soil with grass/shrub vegetation was used over land in the Noilhan-Planton (2 soil-layer force/ restore) surface energy budget. The horizontal motion fields for 1 pm and 4 pm local are plotted in figure 3. In order to improve computational efficiency, a longer timestep was used for the relatively uneventful morning hours. At 1 PM local (elapsed time = 5 hours) plots, surface heating (low-mid 90's F) induces a fairly strong sea breeze (SB) front, best deduced from the streamline fields. There is also a classic cold imprint and divergent flow from Lake Okeechobee. The w vertical cross sections (not shown) show that full solenoidal circulations develop at both coasts, and a very intense dry convective "cell" explodes along the SB front further north. Because of the lack of moisture/convective adjustment, this circulation is believed to be too strong and not very realistic looking late in the simulation.

The next level of complexity will be to obtain sufficient supercomputer time to run the model with the moisture/convective adjustment on the same 12 GMT 25 August 1975 case and then use the "gribit" GRIB decoder (completed in September 1995) to initialize ARPS with non-homogeneous 3-D fields from the operational Eta/Meso model. Then we will try to increase the realism of the simulations by using the high-resolution land cover/use, soil/vegetation databases from the South Florida Water Management District (SFWMD). The Center for Analysis and Prediction at the University of Oklahoma (where ARPS was developed) has offered to assist us with configuring the model for the more complex simulations later this year.

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References

Cunning, J.B. and M. DeMaria,1986; An investigation of the development of cumulonimbus systems over south Florida. Part I: Boundary layer interactions, Monthly Weather Review, 114, 5-24.

Cunning, J.B., H.W. Poor and M. DeMaria,1986: An investigation of the development of cumulonimbus systems over south Florida. Part II: In-cloud structure, Monthly Weather Review, 114, 26-39.

Powell, M.D., S. H. Houston, and T. Reinhold, 1995: Hurricane Andrew's landfall in South Florida: Part I: Standardizing measurements for documentation of surface wind fields. Accepted, Weather and Forecasting.

Baseline Information on the Quality of Nearshore Waters of the Florida Keys: Identifying Trends and Variability

William Miller, The Nature Conservancy, Florida Bay Watch Program

Nearshore waters of the Florida Keys have been little studied. A large information gap exists for this habitat in the south Florida ecosystem. The Nature Conservancy's Florida Bay Watch volunteer program initiated a project using trained volunteers to collect water quality data at canals, harbors, and other nearshore areas along the Florida Keys to help fill this void. The objectives of this ongoing project are to develop a dataset that: 1) quantifies the spatial and temporal variability of water quality in nearshore areas of the Florida Keys, 2) identifies areas of potential impact of Florida Bay water quality on resources of the Florida Keys National Marine Sanctuary (FKNMS), and areas of potential impact of Florida Keys nearshore water quality on resources of Florida Bay, and 3) provides an important baseline to monitor changes in waters quality in nearshore areas of the Florida Keys, especially as changes in sewage disposal practices of the Keys are implemented under the FKNMS management plan. The following results were expected: 1) dredged canals would contain high nutrient levels, concentrated from adjacent On-site Sewage Disposal Systems (OSDS), 2) overall, canal water quality would be degraded relative to water quality at natural/non-dredged shorelines, 3) water column nutrient levels at dredged canals would increase after rainfall events, and 4) water quality at Middle Keys sites will reflect Florida Bay influence more than sites in the Upper or Lower Florida Keys.

Volunteers for this project are trained in basic oceanographic sampling methodologies, including instrument calibration and the collection and handling of water samples for analysis of nutrients and chlorophyll. To ensure the integrity of the data, a program coordinator periodically evaluates the volunteer's sampling routine. All data is quality control checked before entry into a database.

There are currently 25 nearshore water quality stations located at the homes and workplaces of Bay Watch volunteers: 18 bayside and 7 oceanside of the Keys. Eight of the stations are at open-ended

http://www.aoml.noaa.gov/flbay/hydro95.html (9 of 24)9/10/2007 2:32:37 PM http://www.aoml.noaa.gov/flbay/hydro95.html dredged canals, two are at plugged dredged canals, four are at boat basins, and eleven are at natural/non- dredged shorelines. Fifteen of the stations are in the Upper Keys, five are in the Middle Keys, and five are in the Lower Keys. Sites vary in many aspects including water depth, flushing rates, surrounding foliage, and number and type of adjacent OSDS. Most sampling is done from docks or seawalls, however, some sampling is done up to 100 meters offshore. Samples for each station are consistently taken from a marked location for which a GPS position has been recorded.

Water quality stations are sampled at the volunteer's convenience twice a week, at any one low and one high tide, year round. The following information is recorded on a standard data sheet: station number, date, time, tide, Beaufort number for wind and seastate, wind direction, current strength and direction, secchi depth, water color, sea surface temperature, specific gravity, sea surface salinity, and rainfall in the last 24 hours. In addition, volunteers collect and store water samples to be analyzed for total nitrogen, total phosphorus, and chlorophyll a content. Analysis for nutrients and chlorophyll is conducted at the Southeast Environmental Research Program's water quality laboratory at Florida International University, in Miami.

Nearshore water quality sampling began in June 1994 and is ongoing. The following ranges of water quality parameters have been observed thus far: a)secchi depth - 0.1 to 6 meters, b) temperature - 14.00 to 41.50 degrees Celsius, c) salinity - 0.0 to 59.1 parts per thousand, d) total nitrogen - 8.11 to 263.34 micromolar, e) total phosphorus - 0.06 to 4.62 micromolar, f) chlorophyll a - 0.00 to 12.89 microgams per liter. The extremes of temperature were recorded at stations with depths less than 0.50 meters. Total nitrogen tends to be higher at natural/non-dredged shorelines in the Upper Keys than at similar sites in the Lower and Middle Keys. This may possibly be from the influence of freshwater drainage into northeast Florida Bay. As expected, total nitrogen is also higher on average in dredged canals than at natural/non-dredged shorelines. Total phosphorus and chlorophyll a are typically low at most stations, with the highest average concentrations being recorded at dredged canal sites. While total nitrogen and total phosphorus concentrations increase sharply at some stations following rainfall events, this pattern is not consistent within or among stations. Overall, water quality in nearshore areas of the Florida Keys is more variable spatially than temporally.

Nearshore water quality sampling by the Florida Bay Watch program will likely continue in the Florida Keys for at least the next two years. Funding has been secured to expand the project to 30 sampling stations, and volunteers to man these stations are presently being recruited As this dataset and the spatial and temporal coverage of water quality sampling grow, we will be better equipped to characterize the spatial and temporal variability of water quality in nearshore areas of the Florida Keys, and to understand the factors that influence this variability. This dataset will also be an invaluable tool for resource managers to guage their efforts at improving water quality in the Keys.

Dynamics of Groundwater, Surface Water and Salinity Related to the Mangrove/Marsh Ecotone

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William K. Nuttle, Bernard J. Cosby, University of Virginia

The coastal mangrove ecosystem in South Florida and associated nearshore areas are subjected to the mixed influences of climate, sea level and freshwater hydrology. In general, coastal hydrology is "driven" by climatic and oceanographic processes, which operate at the largest scale (i.e. the boundaries of the landscape). The effects of changes in climate and sea level cascade through the scale of hydrologically-defined landscape elements (i.e. drainage basins) to the smallest scale, ecologically- defined elements contained within them. One can conceive of hydrological conditions that vary across the landscape and in time as a hydrological "signal". Hydrological conditions experienced within an ecological element are characteristic of the ecosystem that occupies that element. Here, the meaning of the term "characteristic" includes, but is not necessarily limited to, the following: 1) hydrological conditions are integral to some maintenance function in the ecosystem; 2) succession involves the co- evolution of hydrological conditions in time; 3) infrequent, extreme hydrological conditions impose a disturbance on the ecosystem.

Hypotheses

This research tests the hypothesis that changes in coastal hydrology, caused by rising sea level and changes in freshwater discharge related to climate change and water management, contribute to changes in vegetation at the mangrove/marsh ecotone. Two corollary hypotheses guide the work. The first is that hydrological conditions that characterize the mangrove/marsh ecotone are sensitive to fluctuations in sea level and the flow of freshwater from inland areas to the coast. This hypothesis is being tested by examining historical hydrological and climatological data and by constructing and testing physically- based hydrology simulation models. The second hypothesis is that there is an unique set of hydrologic conditions that characterize the location of the mangrove/marsh ecotone. This hypothesis is being tested by an interdisciplinary investigation of conditions along several transects spanning the transition from the coast into a freshwater marsh, each of which are subject to different hydrologic endpoints and therefore having different spatial distributions of hydrologic conditions through the ecotone.

Methods

The main thrust of hydrological research so far has been aimed at testing the hypothesis that hydrological conditions characteristic of the mangrove/marsh ecotone are sensitive to fluctuations in sea level and the flow of freshwater from inland areas to the coast. This work is comprised of three major components:

- Analyze the historical record of climate, sea level and hydrology to characterize the variation within each time-series and the cross-correlations between series. Both intra-annual and inter-annual variation are being examined. Significant cross-correlations may be evidence of an underlying physical process at work.

- Construct hydrologic simulation model(s) to relate forcing by climate, sea level and freshwater

http://www.aoml.noaa.gov/flbay/hydro95.html (11 of 24)9/10/2007 2:32:37 PM http://www.aoml.noaa.gov/flbay/hydro95.html discharge at the landscape scale to the hydrological signal at the scale of an ecological landscape element. The model(s) will be physically-based and thus represents a hypothesis about the processes chiefly responsible for determining hydrological conditions across the landscape.

- Monitor the hydrologic signal along transects through the transition from the coast into freshwater marshes. This comprises a mesoscale network as there are fewer long-term hydrological monitoring sites than ecological landscape elements. Data collected from this network will be used to test the hydrological model, and they will be used to relate the hydrologic signal to the vegetation in interdisciplinary field studies.

A fourth component is aimed at testing the hypothesis that there is an unique set of hydrologic conditions that characterize the location of the mangrove/marsh ecotone. This is basically a correlative study of hydrologic conditions and species abundance along transects through the mangrove/marsh ecotone. Data collected at mesoscale hydrological monitoring stations will be summarized into a set of candidate indices, such as hydroperiod, range of water level fluctuation, annual mean depths, mean and range of salinity, etc. The assemblage of vegetation will be characterized by data obtained from vegetation plots in the vicinity of the monitoring stations. We will examine the correlation between the hydrological and the vegetative indices for the hydrological indices that correspond most closely to the position of the ecotone, as has been done by in the freshwater marshes. The gradients of hydrologic conditions differ among the transects; therefore failure to find a common set of hydrologic indices characteristic of the ecotone argues for the null hypothesis.

Summary of Results to Date

Historical data

Retrospective analysis has begun on 40 years of monthly data related to the water budget of Shark Slough. These data include evaporation, overland flow, water levels, precipitation and sea level for the South Florida. Both intra-annual variation (i.e. hydroperiod) and inter-annual variation are being examined. From preliminary results, It appears that sea level exerts no influence on hydrology in Shark Slough, even at P35. On the other hand, neither water management nor climate predominate in their influence on hydroperiod, which implies that variability due to climate must be considered in assessing the probable effects of changes in water management.

Hydrological models

Progress in this area has been made on two separate modeling initiatives. The first is a combined surface/ groundwater wetland hydrology model, mainly for use in analyzing the long term water balance data from Shark Slough (Nuttle 1993). This model is implemented as a 1-D finite element code with the one dimension oriented along the axis of Shark Slough from Tamiami Trail to the Shark River estuary. The second is FATHOM, a mass balance model of water and salt in Florida Bay, described separately.

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Seventeen hydrologic monitoring stations have been installed along four transects spanning the coastal mangrove/marsh complex and terminating in the inland freshwater marshes; Chatham River, Lostmans River, Shark River, and south in the C-111 area bordering on Florida Bay. The monitoring at each site includes depth of surface water, hydraulic head in the surficial aquifer, and salinity in the aquifer, the soil and surface water. These data are recorded electronically in the field and transmitted to the Beard Center by radio telemetry.

Outlook for Remaining Work

This research was initiated as part of the Global Climate Change Research program, which may not survive into the next budget year. It is uncertain at this time whether work on hydrology and climate in the estuarine areas will continue and how it will be supported if it does. Assuming that is does, there are four objectives for further work.

The first objective is to complete the retrospective analysis of historical hydrology data that has started with the Shark Slough water budget. A number of issues must be investigated, for example issues arising from non-guassian distribution of some of the data, before the statistical analysis can be considered complete. Also, it may be of interest to apply the same analysis techniques on the shorter time series in Taylor Slough and along the eastern Park boundary to examine the effects of experimental water deliveries.

The three other objectives relate to detailed, process-level studies to be conducted along the study transects now that the hydrological monitoring stations are in place. We are encouraged by the progress we have made in developing the mass balance model for Florida Bay, FATHOM, and we propose to modify and parameterize this model for the spatially complex estuarine areas along the west coast. Next and related to this objective, we are now beginning a project to collect data on salinity, tidal currents and freshwater discharge along the Shark River/Harney River transect. This effort includes detailed sampling, in conjunction with vegetation studies along a transect through the mangrove/marsh ecotone, for the purpose of investigating fluxes of water and solutes in periodically inundated areas. Finally, we propose to study groundwater flow by using geochemical techniques, including stable isotopes, to delineate flow paths and estimate residence times. This approach can be used to address questions of inter-basin flows between Shark Slough and the headwaters of Taylor Slough, beneath the Rocky Glades, and also to study groundwater discharge into estuarine areas.

Freshwater Flows into East Florida Bay

Eduardo PatinoT, U.S. Geological Survey, 9100 N.W. 36th Street, Suite 107, Miami, FL 33178.

http://www.aoml.noaa.gov/flbay/hydro95.html (13 of 24)9/10/2007 2:32:37 PM http://www.aoml.noaa.gov/flbay/hydro95.html Florida Bay, home to several endangered species, is a valuable breeding ground for marine life and an important recreational and sport fishing area. Florida Bay (fig. 1) encompasses about 850 square miles in total area with an average depth of less than 3.5 feet. It is bordered by the mainland portion of Everglades National Park to the north, the Florida Keys to the east and south, and is open to the Gulf of Mexico to the west. During the last decade, Florida Bay has experienced algal blooms and seagrass die- offs which are signals of ecological deterioration that has been attributed to an increase in salinity and nutrient content of bay water. Salinity and nutrient content are directly related to the amount and quality of freshwater that enters the bay and to flow patterns within the bay. Restoration of the Florida Bay ecosystem requires a better understanding of the linkage between the amount of water and nutrients flowing into the bay and the salinity and quality of the bay environment.

As part of the South Florida Ecosystem Program, the U.S. Geological Survey, in collaboration with Everglades National Park, the U.S. Army Corps of Engineers, and the South Florida Water Management District, is conducting a study to measure flows into east Florida Bay. Information from this study will be used in conjunction with data from other studies to help determine the effects of changes in water deliveries to Everglades National Park on the Florida Bay ecosystem. Flow into Florida Bay is closely related to sediment transport, salinity, and chemical characteristics of the bay, which in turn, determine and interact with biological characteristics. Additionally, freshwater-inflow data will be used as input to hydrodynamic models of Florida Bay, for calibration of hydrologic models of the mainland, and for water-budget determinations for south Florida--all of which are essential elements for resource management and the ecosystem restoration.

Prior to the development of currently available acoustic instruments, it was very difficult to gage flows in streams discharging into Florida Bay. Standard methods for field data collection and flow computations are impractical and inaccurate because of the low velocities, flow reversal, and bi- directional flow in which high-salinity water flows inland under freshwater flowing out to the bay (fig. 2). With today's state-of-the art acoustic instrumentation, such as the Acoustic Velocity Meter (AVM) and the Acoustic Doppler Current Profiler (ADCP), it is possible to accurately gage flows in this environment because of the ability of these instruments to quickly measure low or rapidly changing water velocities, even during stratified or bi-directional flow. AVM systems have proven to be accurate instruments in the measurement of water velocities along a horizontal plane across stream and can be permanently installed to collect continuous velocity data that, along with water-level data, are used to produce continuous records of discharge.

ADCP instruments are used to measure water velocities in three dimensions. These measurements are then used to calculate the total flow through a stream section at a given time. The ADCP uses the Doppler shift from four acoustic beams sent downward in set angles to measure the velocity of water, depth, and distance traveled across the stream transect. Field measurements made with the ADCP's are used to develop relations between AVM velocities and discharge at gaged sites.

With the assistance of Everglades National Park, discharge measurements were made with ADCP's near the mouths of the major streams flowing into Florida Bay. Results of these measurements verified the applicability of ADCP's for discharge measurements under these environmental conditions, provided

http://www.aoml.noaa.gov/flbay/hydro95.html (14 of 24)9/10/2007 2:32:37 PM http://www.aoml.noaa.gov/flbay/hydro95.html data on high flows into the bay, and helped in the understanding of flow patterns for each of the measured streams.

Project plans are to instrument selected streams flowing into Florida Bay with AVM's and temperature and specific conductance sensors in order to measure most of the total freshwater flow from the mainland into the bay. Sites are located along the mainland coast of east Florida Bay and represent most of the freshwater flowing south into the bay from Taylor Slough and the C-111 Canal basins. Three of these sites (Trout Creek Canal station and two C-111 Canal stations) are instrumented and maintained by Everglades National Park (fig. 1). Monthly ADCP discharge measurements are planned for rating AVM systems, and monthly collection of water samples are planned for total nutrient analysis. This work will be coordinated with activities from other agencies and institutions who need simultaneous flow data during biological or chemical samplings.

A Comprehensive Groundwater Modeling System for Evaluating the Impacts of the C-111 Canal on Regional Water Resources

David R. Richards, Hsin-chi J. Lin, US Army Engineer Waterways Experiment Station.

Introduction

The Jacksonville District (SAJ) of the US Army Corps of Engineers is interested in studying surface and groundwater hydrology in the area of south Florida affected by the operations of the C-111 drainage canal. The area of interest extends from the Tamiami Canal south to Florida Bay and spanning the entire width of Florida. Water resources in the area consist of coupled surface and groundwater systems that, depending on the hydroperiod, could be dominated by either system individually. There are a wide variety of local concerns that have mutually exclusive interests in the future operations of Corps projects in south Florida, so solutions to the water resources problems will have to be optimized against competing interests. A highly viable means of achieving this goal is the development of a comprehensive modeling system that includes all of the critical hydrologic processes in south Florida.

A multi-year effort is under way to develop such a system for south Florida. The size of the problem is quite large and the complexity of the hydrologic processes are significant. However, a significant amount of work has already been accomplished in the development of the Surface water Modeling System (SMS-formerly FastTABS) and the Groundwater Modeling System (GMS). Each modeling system addresses in great detail the needs of the separate parts of the hydrologic cycle. Indeed, a significant effort was made in their development to ensure that each application used consistent data structures so that the models could be combined or connected at a later data. The C-111 project presents an opportunity to apply all of this technology on a project that requires a thorough modeling effort throughout the hydrologic cycle.

http://www.aoml.noaa.gov/flbay/hydro95.html (15 of 24)9/10/2007 2:32:37 PM http://www.aoml.noaa.gov/flbay/hydro95.html Prototype

Current knowledge of the C-111 region indicates that the hydrologic system is quite complicated with large portions of the water existing in either the surface or groundwater form depending on the hydroperiod. There is also a free exchange of salinity between certain surface and groundwater systems that varies with hydroperiod. As a result, a meaningful application of surface and groundwater models in this region must have flow and salinity transport coupled as it passes between surface and groundwater. Since there are active withdrawals and rediversions by man-made structures and practices, a truly state- of-the-art modeling system is required. Given the geometric and hydrologic complexity of the problem, coupled multi-dimensional models of both surface and groundwater resources are necessary for meaningful tools that will address the important water resource issues.

Comprehensive Modeling Approach

Due to the geographic, climatological, and hydrologic attributes of the C-111 project, each portion of the hydrologic cycle needs to be addressed in the modeling in great detail. At a minimum this requires a system that can route riverine discharges throughout the C-111 canal system, a density-driven hydrodynamic modeling system capable of multi-dimensional riverine and estuarine analysis, and a three-dimensional density driven groundwater modeling system. Additionally, there is a need for specific, intensive field data that will be used in the verification of the surface and groundwater models. This study involves the collection of such data and the verification of the surface and groundwater models.

Groundwater Processes

Groundwater processes in south Florida have a significant impact on regional water resources. When water levels are maintained at lower than historical levels, it is possible to provide the maximum level of flood protection. However, lower groundwater levels can result in large groundwater recharge rates that almost entirely eliminate surface water runoff into estuarine areas such as Florida Bay. This can have significant negative impacts in Florida Bay due to the high evaporation potential. With a large evaporation potential and suppressed freshwater runoff into Florida Bay, it is possible to create hypersalinity problems. Hypersalinity is currently a problem in Florida Bay but it is not yet known how much of this is a natural phenomenon or what impact the management of C-111 has on the degree of the problem. Numerical models of surface and groundwater processes are the most effective means of evaluating if C-111 management strategies can be developed to maintain flood protection and allow sufficient runoff to enter Florida Bay to minimize the hypersalinity problem.

Groundwater Modeling Objective

The objective of the groundwater modeling effort is to create a regional groundwater model that can be used to study various C-111 management strategies. The developed groundwater model will be able to predict regional groundwater flow and salinity transport. The model will be constructed so that all of the

http://www.aoml.noaa.gov/flbay/hydro95.html (16 of 24)9/10/2007 2:32:37 PM http://www.aoml.noaa.gov/flbay/hydro95.html major users of water in south Florida (cities, agriculture, the Everglades, etc.) are included.

Groundwater Modeling Approach

A regional groundwater model of south Florida will be constructed using the Department of Defense Groundwater Modeling System (GMS). GMS is the standard groundwater modeling system within the Department of Defense for conducting hazardous and toxic waste contamination investigations associated with the environmental restoration of military bases. As such, the system has a high degree of sophistication for modeling a wide variety of groundwater flow and transport problems. The GMS contains all of the necessary ingredients required to successfully model groundwater in south Florida. These include a comprehensive graphical user interface, a complete database management system for storing and accessing surface and subsurface data, a suite of subsurface conceptualization tools for developing solid models of the stratigraphy, and a variety of flow and transport models with pre- and post-processing capabilities including an extensive suite of visualization tools. While the GMS is available for both personal computers and UNIX workstations, this application will require the use of a fast UNIX workstation.

Based on available surface and subsurface data, a complete hydrogeologic conceptualization of the region will be performed. This will include an analysis of the subsurface stratigraphy, estimation of hydrogeologic parameters, identification of groundwater recharge areas and rates, and an analysis of pumping data from a variety of sources. Once this is completed, a 3-D finite element model (FEMWATER) will be constructed. FEMWATER is a variably-saturated model that includes density- driven (salinity) transport. During this project, FEMWATER will be improved by directly coupling flow and transport between the surface and groundwater. This will be accomplished by accounting for mass transfers of water and salinity between the surface and subsurface within the model. The improved FEMWATER will address the problem frequently encountered in the canals of south Florida where pumped groundwater is used to maintain canal levels which tend to drain back into the aquifers depending on hydrologic conditions. This is an essential feature that is not available in other modeling systems and is required to get accurate answers in this region.

Groundwater Model Coverage

The groundwater model will extend from the Tamiami Canal south including the entire tip of south Florida. This will include both Florida and Biscayne Bays. The Tamiami Canal is identified because it is an area of well documented water levels that can serve as boundary conditions. The mesh will extend offshore to areas where salinity conditions are well known. For the existing and plan conditions, the groundwater model will take salinity boundary conditions from available surface and subsurface data and numerical surface water models.

Surface Water Model Connections

A connection between surface and groundwater models is essential to correctly model South Florida

http://www.aoml.noaa.gov/flbay/hydro95.html (17 of 24)9/10/2007 2:32:37 PM http://www.aoml.noaa.gov/flbay/hydro95.html physical processes. This connection will occur in two ways. First, there is a connection between the open coastal areas which will be defined by the surface water models. These models will provide spatially distributed salinity values that will be used as boundary conditions for the groundwater model. Second, the canal areas in the interior of Florida will connect surface and groundwater within the FEMWATER model. In the first case, surface and groundwater models will be run separately but connected through boundary condition passing. In the second case, the interaction will be directly coupled within a single model. At this stage of model development, it is not necessary to directly couple all models in a single model.

Production Runs

Once the groundwater model is verified to the existing conditions, a total of 10 different operational scenarios will be simulated. These may include different meshes for each to test various geometric changes to the canal system including rediversions of C-111 waters. Other simulations could include maintaining different water levels for the purposes of evaluating recharge efficiency and the ability to get freshwater runoff to Florida Bay. Some of the simulations may include projecting impacts from extreme weather conditions on the existing and plan conditions. Likely simulations include long term droughts and extremely wet conditions such as hurricanes.

Hydrodynamic Modeling for Evaluation of the Impacts of the C-111 Canal on Regional Water

Lisa C. Roig, David R. Richards, US Army Engineer Waterways Experiment Station.

Introduction

Hydrodynamic modeling, as it is defined here, is the riverine and estuarine simulation that is important to the management of various surface water systems in south Florida. For the purposes of this project, the dominant concern is Florida Bay. Florida Bay is a shallow, semi-enclosed lagoon system that has an unusual distribution of emergent and partially submerged mudflats, islands, and mangrove swamps. The bay itself is essentially an interconnected assemblage of shallow basins that are connected by narrow navigation passages, and by flow through the mangrove stands and intermittent flow over the mudbanks. Observations of water color and turbidity indicate that the circulation and mixing of water particles in the Bay are complex phenomena. Hydrologic inputs to the Bay such as freshwater releases from C-111 and storm based rainfall events have localized affects that are spatially and temporally heterogeneous. The water column is generally quite shallow and vertically well mixed throughout the Bay. Under unusual circumstances salinity stratification has been observed in some of the basins, but these isolated events probably do not have a major impact on the overall circulation of the Bay.

Objectives

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The objectives of this study are 1) to develop a two-dimensional, vertically averaged model of hydrodynamics and salinity transport in Florida Bay; 2) to use the model to understand the impacts of alternative freshwater release scenarios on circulation and salinity distribution in the Bay; and 3) to provide the model data sets and user documentation to local resource agencies for in-house modeling studies.

Technical Approach

To model the effects of alternative freshwater releases on the circulation of Florida Bay, one must resolve the horizontal bathymetry of the basins, the partially submerged mudbanks, the mangrove swamps, and the coastal boundaries. Since the water column is generally well mixed, a two-dimensional, vertically averaged model of circulation in the Bay is adequate to simulate the majority of the hydrodynamic phenomena that have been observed. The equations that describe horizontal circulation and mixing in the Bay are the vertically averaged shallow water equations, the advection-dispersion equation for dissolved salts, and an equation of state relating salinity concentration to fluid density. The model to be used must be capable of resolving the complex horizontal distribution of mudflats, islands, and mangrove swamps that control circulation in the interior of the bay. The model must include an algorithm for describing the flooding and draining of the islands and mudbanks as water levels rise and fall. One modeling system that incorporates these equations and these capabilities is the TABS-MD numerical modeling system that was developed and is maintained by the U. S. Army Corps of Engineers Waterways Experiment Station (WES).

At the heart of the TABS-MD system are the finite element model for two-dimensional, vertically averaged free surface flows known as RMA2 and the finite element model for two-dimensional transport of dissolved constituents known as RMA4. These models were originally developed by Dr. Ian King at Resource Management Associates (RMA) under contract to WES. The models have been maintained and improved by the staff at WES, and are incorporated into the TABS-MD system as RMA2-WES and RMA4-WES. A sophisticated, user friendly, graphical user interface (GUI) known as the Surfaces Water Modeling System or SMS (formerly FastTABS) has been developed at WES to facilitate the pre- processing of input files and the post-processing of model outputs. This GUI allows the user to visualize model results in a variety of ways, including contour maps, vector maps, and animated displays of time dependent solutions. The user documentation and tutorial guides for these models exist and have been extensively field tested

Florida Bay is unusual because the horizontal salinity distribution may have a significant effect on the horizontal circulation in the Bay. Many vertically well-mixed estuaries are strongly driven by tidal forces and wind forces so that the density driven component of the currents is negligible when considering horizontal circulation. RMA2-WES and RMA4-WES have been widely applied to these types of estuaries. Previous versions of these models effectively decoupled the hydrodynamic calculations from the salinity calculations, which did not have any adverse effect on the accuracy of the solution for most vertically well mixed estuaries. Because Florida Bay is expected to have a significant horizontal response to salinity induced density gradients, the algorithm is being modified to couple the

http://www.aoml.noaa.gov/flbay/hydro95.html (19 of 24)9/10/2007 2:32:37 PM http://www.aoml.noaa.gov/flbay/hydro95.html salinity calculations with the hydrodynamics.

Simulating the propagation of tides through the mangrove swamps is highly dependent upon the parameterization of the friction terms in the momentum equations. WES has been actively involved in the development of new formulations for frictional resistance to flow through emergent vegetation. To properly simulate the flow through the mangrove stands requires the incorporation of a dynamic friction formulation to replace the usual Mannings relationship. An initial version of this algorithm has been successfully tested in a separate study.

Offshore water level boundary conditions will be supplied by an existing numerical model of the Gulf of Mexico, Caribbean Sea, and Atlantic Ocean. Ultimately, the RMA2-WES model will extend from the west coast of Florida, throughout the Keys and stop north of the C-111 discharge. Up to three freshwater release scenarios will be simulated, including a base condition which will be verified to a data set that is yet to be selected. The simulation period will be on the order of a season (several weeks). The results of the simulations will be documented and the modeling methodology will be fully described.

Visual Mapping of Water Quality in Florida Bay and Adjacent Waters

Bill Sargent, Courtney Westlake, Florida Department of Environmental Protection, Florida Marine Research Institute, Coastal and Marine Resource Assessment Section, 100 Eighth Avenue Southeast, St. Petersburg, Florida 33701-5095, Telephone (813) 896-8626; Dave Eaken, Florida Department of Environmental Protection, Florida Marine Research Institute, South Florida Regional Laboratory, 2796 Overseas Highway, Suite 119, Marathon, Florida 33050-3513, Telephone (305) 289-2330

Since March 1994, we have conducted monthly aerial surveys of Florida Bay and adjacent regions to determine the extent and distribution of turbid or colored waters. The resultant maps are incorporated into an ARC/INFO geographic information system (GIS) for comparative analyses and production of display maps.

Each month observers fly over the study area in a small aircraft. A set of 16 subjective categories is used to identify different types of water masses from each other. As the actual number of differently colored water masses observed at any one time can be immeasurable and the subtle differences which visually distinguish them from each other can be impossible for a human to accurately detect, each color category used on the maps incorporates a broad range of related water types. Because each person has their own interpretation of color and texture, it is difficult to standardize observations based on verbal descriptions. It is only with experience in the field that the observation team members have been able to standardize this classification. To maintain consistency among surveys the same two main observers are used each month. The observers constantly confer with each other during the survey but record their own individual observations. Water categories are assigned as a consensus among observers during

http://www.aoml.noaa.gov/flbay/hydro95.html (20 of 24)9/10/2007 2:32:37 PM http://www.aoml.noaa.gov/flbay/hydro95.html drafting of a master map after each flight. Although this methodology is subjective we believe it is an effective means for obtaining a snapshot of the distribution of water color conditions in the region and portraying these distributions in a readily interpretable manner. The colors depicted on the maps are not the actual water colors observed, but are meant to be a representation of the differences in the water types observed in Florida Bay and the adjacent Keys. The objective of the aerial survey is to map the distribution of visually distinct water masses during a specific instant in time.

The geographic region currently covered by the survey extends from Key Largo southwest to Big Pine Key, including the reef tract south of the Keys, then northward from Big Pine Key to Ponce de Leon Bay, back south to Cape Sable, and east to Barnes Sound. Most of the bays and lakes along the northern shore of Florida Bay, including Lake Ingraham are surveyed. In the future, the survey region might be expanded westward to Key West. This survey expansion will be accompanied by an expansion of a ground truthing effort.

A joint effort between the Florida Marine Research Institute and The Nature Conservancy Bay Watch volunteer program is collecting water samples and performing analyses to determine the composition of the major water masses observed. A series of 6 fixed location stations are sampled during the aerial survey. Up to 24 additional stations are sampled the following day. The locations of these stations are determined based upon locations of water masses of interest. These efforts are discussed elsewhere in these proceedings. Summarized excerpts of these water quality data are incorporated into the GIS for analyses and display on maps produced for public distribution. These data are used in comparative analyses with data from other research efforts being conducted by the Florida Marine Research Institute and discussed elsewhere in these proceedings.

GIS is proving to be an effective mechanism to promote data sharing and the combining of data from different research efforts to allow for investigation of the ecosystem from an integrated perspective. The GIS is also used to mass produce informative maps which are distributed to scientists, resource managers, environmental policy makers and the concerned public on a routine basis. In order to provide the public with information about Florida Bay, the Florida Department of Environmental Protection and The Nature Conservancy Bay Watch volunteer program are collaborating on projects to place long-term displays in public places and provide the news media with appropriate material for incorporation into news stories.

A summarized version of the colored water maps condenses the 16 water categories into five major classifications. The five classifications are; turbid water caused primarily by sediment in the water, turbid water caused by sediment and microalgae in the water, turbid water caused primarily by elevated levels of microalgae in the water, water which is stained brown due to its natural association with nearby wetlands, and water with minimal or background levels of turbidity. These five classifications represent the five major types of water quality situations observed in Florida Bay.

Both the summarized and detailed versions of the maps are made available to all individuals who request them. A mailing list is maintained to automatically provide interested individuals with new monthly

http://www.aoml.noaa.gov/flbay/hydro95.html (21 of 24)9/10/2007 2:32:37 PM http://www.aoml.noaa.gov/flbay/hydro95.html maps as soon as they are available.

Hydrogeologic Aspects of Sewage Disposal in the Florida Keys

E. A. Shinn, Christopher D. Reich, Robert B. Halley, USGS, 600 4th Street South St. Petersburg, FL 33701, Ronald S. Reese, USGS, 9100 N.W. 36th Street, Miami, FL 33178.

Quarterly samples of Groundwater from 45 monitoring wells in Pleistocene limestone beneath Florida Bay, the reef tract and on the Keys, was sampled and analyzed quarterly. Well depths range from 5 to 20 m. Nutrients NO2, NO3 and NH4 in the offshore ground water were elevated about 10 times that of sea water and NH4 increased progressively up to 40 times that of seawater under coral reefs 8 to10 km offshore. Salinity, except for shallow wells onshore, ranged from 36 to 42 ppt and the waters were generally anoxic. Onshore ground waters were equally saline except in shallow near-surface wells, where salinity measured 10 ppt or less. Fecal bacteria were identified in saline ground water from both onshore and offshore wells.

Subsurface hydrology is controlled by lithology, buried subaerial unconformities, and by Holocene carbonate mud overlying karstic Pleistocene grainstones and reef deposits. Tidal pumping, sufficient to raise water 20 cm above sea level, suggests leakage of nutrients and bacteria into surface marine waters, especially nearshore where there is no overlying Holocene sediment. Higher sea level in Florida Bay causes ground water to flow through the Keys and likely incorporates nutrients and bacteria from the 30,000 septic-tank drain fields and approximately 700 shallow sewage water injection wells. Because flow is toward the reef tract, both natural and anthropogenic nutrients may cause observed blooms of benthic algae and coral diseases.

A Comparison of Mercury in Estuarine Fish: Indian River Lagoon and Florida

Douglas G. Strom, Gregory A. Graves, Florida Department of Environmental Protection, Southeast District Ambient Water Quality Section, Port St. Lucie, Florida.

Three-hundred sixty seven economically important gamefish were collected from two Florida estuaries: Indian River Lagoon in Martin and St. Lucie Counties and Florida Bay. Fish species collected were spotted seatrout, snook, gray snapper, jack crevalle, mayan cichlid, black drum, gafftopsail catfish, pompano, redfish, sheepshead, southern flounder and spadefish. Mercury tissue analyses were performed on edible filets.

Statistical analysis indicated that location was the most significant factor affecting mercury levels.

http://www.aoml.noaa.gov/flbay/hydro95.html (22 of 24)9/10/2007 2:32:37 PM http://www.aoml.noaa.gov/flbay/hydro95.html Several species of fish caught in eastern Florida Bay exhibited an enrichment in mercury with respect to other sample collection areas. a significant portion of the estuarine fish collected in eastern Florida Bay exceed the 1.0 mg-Hg/Kg USFDA "no consumption" health advisory criteria. Mercury levels were especially elevated in jack crevalle from all areas, and in spotted seatrout from northeastern Florida Bay. Estimates of the percentage of fish within an area that may exceed applicable state and federal fish consumption advisory levels are presented.

Current status of project: Final report available November 10, 1995.

Monitoring and Evaluation of Radar Measured Rainfall Estimates Over Florida Bay and the Everglades

Paul T. Willis, NOAA/CIMAS, University of Miami, 4301 Rickenbacker Cswy., Miami, FL 33149.

Objective or Hypothesis

The freshwater input to Florida Bay, directly from precipitation and through flow from precipitation to the north, is a crucial factor in any analysis, or modeling, of the salinity levels in Florida Bay. Because of the convective nature of the rainfall over South Florida, sparse gage measurements only give representative rainfall measurements for long averaging periods -- a month or longer. Any study of shorter time scales requires much higher resolution precipitation measurement. The new digitized and recorded next generation Doppler weather radars (WSR-88D - NEXRAD) at Miami, and eventually Key West, will be capable of producing rainfall estimates over the entire Florida Bay area at a time and spatial resolution not previously possible. The NWS algorithms used to convert radar reflectivity to rainfall rates were developed largely for mid-latitude subtropical regimes, and are not always appropriate for the more tropical rainfall in South Florida.

To fully exploit the the capabilities of the new radars for hydrological purposes over Florida Bay and the Everglades, their rainfall estimation algorithms must be tuned for the tropical South Florida conditions. Despite its tremendous promise estimate of rainfall from radar data is not without problems. Many of these problems can be solved. It is the objective of this research project to tune these algorithms based on existing rain drop size distribution (DSD) data, and on new drop size distribution data collected with aircraft and on the ground in the Florida Bay/Everglades area. The goal is to produce the best possible high resolution radar rainfall product possible for the Florida Bay/ Everglades area for use by all Florida Bay researchers.

Methods and Timing

Funding was received, and this project commenced only in the middle of this September. The following tasks are underway:

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NWS radar data are being archived for use and evaluation. Data are being collected for several case studies to evaluate whether the raw radar scan data, or a modified partially processed product is the most appropriate for an accurate Florida Bay rainfall atlas.

Flights will be conducted starting late September to collect airborne rain DSD data for input into a probability matching methodology to estimate rain rate from radar reflectivity measurements.

Existing rain DSD data are being compiled and arrangements are being made to collect surface rain DSD data in the Everglades/Florida Bay area.

The radar rain estimates will be compared and evaluated using all available gage data.

Outlook for Remaining Work

We plan to collect data at the end of this rainy season and concentrate on the transition into next summers rainy season.

Last updated: 07/15/98 by: Monika Gurnée [email protected]

http://www.aoml.noaa.gov/flbay/hydro95.html (24 of 24)9/10/2007 2:32:37 PM Mangrove Ecology-1995

Mangrove Ecology

1995 Abstracts

Patterns of Vegetation and Mangrove Die-back on Florida Bay Keys

Thomas V. Armentano, Everglades National Park, South Florida Natural Resources Center, 40001 State Road 9336, Homestead, Florida 33034-6733.

Anecdotal reports of dead and dying mangroves on islands in Florida Bay began to appear in the late 1980s and continued in following years. Aerial overflights in 1992 confirmed that, particularly in island interiors, stands of dead mangroves were common in eastern and central Florida Bay. However little information was available on the extent of the mortality pattern, its rate of development and its causes. To address these uncertainties, several studies were begun involving related aspects of the mangrove mortality concern. The present work has concentrated on determining the current composition and structure of the vegetation on selected islands and inferring the recent past vegetation from aerial photographs and the presence of woody material and other field evidence of earlier plant communities. From these data, relationships to hurricanes and droughts will be developed that should help determine the causes for the time trends in mangrove mortality and recovery that appear to characterize the islands and northern coastal area of Florida Bay.

A literature review suggests that the patterns of mangrove mortality observed in Florida Bay may be driven largely by intrinsic forest stand processes and disturbance interventions largely independent of human activities. Several papers by Lugo and colleagues, indicate that a pattern, possibly cyclic, of mangrove forest development, senescence and recovery appears to characterize some mangrove islands in the Caribbean Sea. Droughts and hurricanes intervene, however, interrupting stand development. Salinas development in island interiors often leads to hypersalinity and consequent accelerated mortality of mangroves creating a pond or basin devoid of vascular vegetation. Hurricanes, in contrast, may destroy forests and shift or deposit large quantities of sediment, thereby rendering islands open to recolonization by mangroves (Craighead, several refs.). This concept has been accepted as an hypothesis to be evaluated at least for islands dominated by mangrove forest or scrub, without discounting the possibility that other factors are involved. Initial inspection of islands from the western, central and eastern portions of the Bay, for example, shows that elevation differences, significantly influence the potential for vegetation development. Thus certain keys may be too low (e.g., most of Club Key) or too high (e.g. Murray Key) to expect the simplified model described above to be valid. Salinity of Florida Bay waters might also affect vegetation patterns by influencing pore water salinity on the islands.

Detailed vegetation inventories have been completed on Clive and Pass Keys (western and eastern Florida Bay, respectively). So far about 30 keys have been inspected either on foot or by low altitude

http://www.aoml.noaa.gov/flbay/mang95.html (1 of 3)9/10/2007 2:32:37 PM Mangrove Ecology-1995 overflights . Low-level photographs of most of these islands were made in 1995 and a photographic series is available dating back to 1935. In general, on many of the islands which aerial inspection revealed as exhibiting various stages of mangrove mortality in 1992, seedlings and twig sprouting of partially dead mangroves can now be seen. Expansion or rapid growth of halophyte cover (e.g., Batis maritima and Salicornia virginica) also is common. The extent to which any of these patterns represents "recovery" and the initiation of a new sequence of vegetation development is unclear, particularly given that the current pattern is quite variable from island to island. Future work will concentrate on further quantitative inventory of present vegetation on selected islands and aerial photograph interpretation. Results will be combined with parallel studies by the Florida Department of Environmental Protection (Marine Research Institute) and National Biological Service in order to better understand underlying causative mechanisms.

Mangrove Mortality in Florida Bay

P. Carlson, S. Brinton, Florida Marine Research Institute; T. Armentano, D. Smith, Everglades National Park; J. Absten, Florida International University.

Widespread mortality of mangroves occurred in Florida Bay during spring and early summer 1991 and again in spring 1992. Black mangroves (Avicennia germinans) growing on keys with shallow, central basins (salinas) appeared to be most severely affected, suggesting that hypersaline conditions in Florida Bay might have played a role in mangrove mortality.

Our investigation focused on the role of climate and porewater salinity in mangrove mortality. Because the mangrove mortality was most acute in spring 1991, we reviewed environmental data for the period from 1987 to the present looking for unique climatic or physical conditions concurrent with mangrove die­off. We assembled temperature, rainfall, and evaporation data from National Weather Service reporting stations in South Florida. Surface water salinity and water level data were obtained from Everglades National Park monitoring program stations at Whipray Basin and Buoy Key, respectively. Water level records for Key West and Vaca Key tide gauges were supplied by the National Ocean Survey.

To hindcast porewater salinities during the 1991 die­off episode, we sampled porewater on two islands every 4 to 8 weeks between May 1992 and August 1993. Dump Key was severely impacted by die­off; Clive Key was not. PVC well screen was used to collect depth­integrated porewater samples from 5 to 35 cm depth at three stations (1,10,and 20 m from shore) along two transects on each island. Chloride and sulfate concentrations were measured each time; sulfide concentrations were measured less frequently.

Temperature, rainfall, and evaporation data indicate that spring 1991 was similar to preceding and following years. Mean maximum temperatures ranged from ca. 24°C in winter to ca. 33°C in summer;

http://www.aoml.noaa.gov/flbay/mang95.html (2 of 3)9/10/2007 2:32:37 PM Mangrove Ecology-1995 no freezes occurred in winter 1990­1991. Biweekly rainfall measured at Flamingo was similar in 1990, 1991, and 1992, and wet and dry season rainfall totals for Flamingo and Tavernier also showed no significant departures from average values during this period. Surface water salinity records for Whipray Basin show hypersaline conditions for most of 1989, 1990, and 1991. However, maximum surface water salinity occurred in fall 1989, and mangrove die­off occurred in spring 1991 and spring 1992, a period when surface water salinity was declining.

Porewater salinity at Clive Key varied from 40 ppt in winter to 49 ppt in summer. At Dump Key, salinity varied from 40 ppt in late winter to 67 ppt in summer. Regression of porewater salinity against tidal inundation frequency resulted in estimates of porewater salinity greater than 90 ppt during periods of infrequent tidal flooding. Mangrove transpiration caused significant increases in porewater sulfate: chlorinity ratios during the spring season.

Frequent tidal inundation in winter 1990­1991 is the single most striking climatic event coinciding with mangrove mortality. In particular, inundation frequencies in December, January, and February were much higher in 1991 than in 1990. As a result of residually high surface water salinity and higher than normal inundation frequency, porewater salinity in low islands within Florida Bay might have exceeded lethal levels for Avicennia. The cause of the shift in winter tidal inundation frequency is not known, but other researchers have described a shift of ca. 10 cm in mean sea level with a quasi­decadal frequency. Small changes in sea level, cyclic or otherwise, might have a pronounced influence on the mangrove communities of low islands and the mainland shoreline of Florida Bay, especially when they coincide with periods of hypersalinity in Florida Bay surface water.

This project addresses question C.2. (Tasks ii and vii) of the Seagrass, Mangrove, and Hardbottom Habitats section of the Science Plan for Florida Bay: "What environmental factors explain the pattern of mangrove die­back within the Florida Bay ecosystem?" On­going studies of mangrove mortality at FMRI include expansion of quarterly porewater monitoring to additional islands and mainland sites, historical GIS analysis of mangrove communities, and analysis of longer­term water level records.

Last updated: 07/16/98 by: Monika Gurnée [email protected]

http://www.aoml.noaa.gov/flbay/mang95.html (3 of 3)9/10/2007 2:32:37 PM Marine Endangered Species - 1995

Marine Endangered Species

1995 Abstracts

Spatial Analysis of Florida Bay

Joan A. Browder, NOAA, National Marine Fisheries Service, Miami, FL; Oren Bass, Everglades National Park, South Florida Natural Resource Center, Homestead, FL; Jennifer Gebelein, Steve Huang, Univ. Miami Rosenstiel School of Marine and Atmos. Sci., Miami, FL.

A spatial analysis of Florida Bay is being conducted that will examine biological distributions in relation to physical variables. The data will be viewed and analyzed as layers of geographical information. Layers of physical data in GIS format are being obtained from Everglades National Park and the Florida Department of Environmental Protection. These data include geographic shoreline configuration at the bay boundaries (mainland and Florida Keys), bottom topography, and bank delineations. Sea level data from which to estimate water depths throughout the bay for specific times of the year and times of the day are being computed initially based on ouput from John Wang's finite element numerical model. Data for overlaying salinity contours for representative days will be obtained from U.S. Geological Survey and others. Information on seagrass beds will be added when this is completed in another National Marine Fisheries Service study.

An aerial survey of the large scale and fine scale distribution of wading birds and other large water birds across the bay is providing the first biological layer of the analysis. The aerial survey is a joint environmental project of the National Marine Fisheries Service and the Miami Air Station of the U.S. Coast Guard. The USCG provides the platform, an HH65 Dolphin helicopter, and a pilot and flight mechanic. Everglades National Park is contributing personnel to the study.

Our first hypothesis is that Florida Bay is a significant feeding area for the same wading bird populations that also feed in the mangrove and freshwater areas of Everglades National Park. Our second hypothesis is that daily and seasonal variations in sea level have a major influence on the accessibility of prey to birds in different parts of the bay and in the bay as a whole.

A major objective of survey is to describe the use of the banks and shallow flats of the bay as foraging areas. We want to know how much the aquatic resources of the bay support wading bird populations, the extent to which daily, lunar, and annual cycles of the tide affect energy flow to the birds from the bay, and how the parts of the bay differ in their support value for the various wading and water bird species.

Wading and water birds, because they can be seen from the air, may be useful as indicators of the productivity of the bay. Information concerning bird distributions may help us better understand and

http://www.aoml.noaa.gov/flbay/mari95.html (1 of 9)9/10/2007 2:32:38 PM Marine Endangered Species - 1995 compare the various parts of the bay. Determining how access to feeding sites is affected by periodic variation in sea level will improve the ability to interpret information on bird distributions in terms of bay productivity.

The periodic variation in water depth on the banks and flats caused by tide and seasonal changes in mean sea level must have a profound effect on aquatic communities. According to Smith and Pitts, tidal amplitude is as great as 35 cm, and the amplitude of annual variation in mean sea level is about 20 cm. Tidal amplitude is greatest in at the western edge of the bay and diminishes by about 2 cm/km moving eastward. By the time tidal waves reach the interior of the bay, amplitude has diminished so much that daily tidal processes have become inconsequential. Substantial changes in water levels in the interior of the bay do occur, but these are associated with processes that occur over an extended period of time. Because they are able to wade only when water depth is below a certain maximum threshold that roughly corresponds to the lengths of their legs, the activities of wading birds provide a means of viewing these dynamic conditions on a broad scale from a biological perspective.

The presence of birds feeding on the banks allows us to confirm or adjust the predictions of tidal stage at specific locations that we make for our flights on the basis of tidal predictions for Flamingo and Lignum Vitae Key (obtained from commercial computer software), adjusted for other locations by means of Smith and Pitts' graph showing the time lag across the bay of the semidiurnal (M2) component of the tide. With this information we intend to develop the capability to predict wading bird usage of banks in specific areas.

Obtaining monthly estimates of species abundance within the bay to compare with results of ongoing surveys in the coastal and freshwater wetlands of Everglades National Park has become another overall objective of our study, because there has been no recent systematic survey or census of wading and water birds in the bay. Published and unpublished information from past censuses of some wading bird species in the bay will allow us to make comparisons with bay abundances in previous years.

Our aerial survey is a census that covers the bay with 1-nautical-mile-spaced transects. We depart from transects to census birds on islands and to identify birds spotted from a distance. Then the transect is re- entered and along-transect flight continued. Every island within the part of the bay covered by the flight is circled. For logistical reasons, four parts of the bay are delineated. We attempt to cover one or more full quadrants on each flight day and to cover all quadrants each month. We cover the entire bay in 3 to 5 flight days, depending upon weather conditions. The transects are oriented north to south, and flights are initiated in the western part of each quadrant in order to be in phase as much as possible with the eastward progression of tidal stage across the bay.

Tidal stages occur at different times in different parts of the bay because tidal wave propagation is slowed by the shallow banks and islands. Low and high tides occur earliest at the western edge of the bay and progress eastward. Tidal patterns in the bay near the Middle Florida Keys are complicated by the influence of Atlantic tides, which differ from those of the Gulf of Mexico. John Wang's computer model takes into account the bottom friction and extreme constriction resulting from drag due to islands

http://www.aoml.noaa.gov/flbay/mari95.html (2 of 9)9/10/2007 2:32:38 PM Marine Endangered Species - 1995 and banks, which cause a phase lag in tidal stage from the southwest boundary northeastward across the bay. The model simulates sea level over the entire bay throughout the lunar cycle and will be very useful in examining our bird data in relation to conditions in the bay at the time of our flights.

In our survey flights, large water birds, including herons, egrets, pelicans, cormorants, and frigate birds, are counted, by species, and their behavior noted. Behaviors include wading or floating in the water, perching on posts or snags over water, roosting in trees, nesting, standing on the ground, standing on the shore at the water's edge, and flying. Birds flying over islands are distinguished from those flying over water.

In summarizing the data or preparing it for spatial analysis, birds loafing or nesting on islands (in trees or on the ground or shore) and on posts, are compiled separately from those wading (and presumably feeding) on interior ponds of the islands or wading (or floating, in the case of cormorants and pelicans) in the bay. The pond and baywater birds also are separated from each other. By compiling the data in this manner, we can examine how the different parts of the bay are being used by the birds at the time of our flights. Nesting birds also will be distinguished separately in recording data so that the temporal and spatial distribution of nesting can be analyzed for each nesting species.

At the present time, 6 months of flights have been made. We hope to continue the study for at least 8 more months to cover the entire year and allow for repeated coverage of the first 2 months, which was a learning and gearing up period. A complete year of observations is important to determine how differences in mean sea level and reproductive activity of the birds affects their use of the banks for feeding. Seasonal changes in mean sea level or nesting activity may also affect the principal islands selected by the birds. We are up to date in entering the data and have developed programs to summarize the data. Thus we are in the process of obtaining quantitative results from the first 6 months of flights.

Our cursory observations suggest that, at least during the summer months, Great White Herons and, to a lesser extent, Great Blue Herons, wade (and presumably feed) on the banks more than any other species. Reddish Egrets, in both red and white phase, have a major presence in the eastermost island chains of the northcentral part of the bay and feed on the shallow banks associated with these islands and also along the shoreline at Snake Bite. Brown Pelicans, Double Crested Cormorants, and, to a lesser extent, Magnificent Frigate Birds dominate the avian fauna in the southcentral part of the bay, roosting in number on the Arsenicker, Buchanan, and Barnes Keys. The cormorants sometimes form large circular rafts of densely packed birds floating on the water. By far the greatest concentration of feeding wading birds that we have seen is on the shallow flats that extend some distance south from the shoreline at Snake Bite. At various times this aggregation has included such species as Great White Herons, Great Blue Herons, Great Egrets, Reddish Egrets, White Ibis, Little Blue Herons, and Roseate Spoonbills. Wading birds are usually seen at low tide on First National Bank in the vicinity of Carl Ross and Sandy Keys, on Nine Mile Bank in the vicinity of the Arsenicker Keys, and on Petersen Bank near Lignum Vitae Key. We have seen Great White and Great Blue Herons feeding far out on banks well removed from islands.

http://www.aoml.noaa.gov/flbay/mari95.html (3 of 9)9/10/2007 2:32:38 PM Marine Endangered Species - 1995 In the future, we hope to acquire information on fish and invertebrate community composition and densities to include as GIS data layer. These data would be examined in relation to physical factors, including the overlap of salinity bands with habitat features such as banks and seagrass beds. Fish data also would be examined in relation to bird densities and feeding, nesting, and roosting patterns.

Research, Monitoring and Modeling of the Endangered American Crocodile Crocodylus Acutus in Florida Bay

Frank J. Mazzotti, Department of Wildlife Ecology and Conservation, University of Florida, 3245 College Avenue, Davie, FL 33314; Laura A. Brandt, National Biological Service Cooperative Research Unit, Department of Wildlife Ecology and Conservation, University of Florida, 117 Newins- Ziegler Hall, Gainesville, FL 32611.

The American crocodile is a federally listed endangered species, whose main population center is in an area Florida Bay likely to be affected by C-111/Taylor Slough and other restoration projects. Although the status of the American crocodile has long been a matter of concern it now appears that the population has stabilized in this region. However, as for other species of wildlife in southern Florida, the survival of crocodiles has been linked with regional hydrological conditions, especially water levels and salinities. Alternatives for improving water delivery into Florida Bay via Taylor Slough and the C-111 system may change salinities and water levels in the receiving water bodies. The purpose of the American crocodile research and monitoring program is to insure the continued survival of an endangered species in a changing environment.

In the Taylor Slough/C-111/Florida Bay system a successful endangered species research and monitoring program should investigate population parameters likely to be affected by alternatives proposed for ecosystem restoration. For crocodiles population parameters most responsive to hydrological conditions are distribution, growth, survival, and nesting effort and success.

The objectives of this project are:

1. To monitor nesting effort (number of crocodiles that attempt to nest) and success (number of nests that hatch) of the American crocodile in Florida Bay.

2. To determine the patterns of growth and survival of crocodiles from nests from different locations and habitats.

3. To evaluate the relationship between salinity and distribution of non-hatchling crocodiles.

Crocodile nesting effort and success will be determined during 1994 and 1995 by searching known and potential nesting habitat in Florida Bay during April and May (effort) and July and August (success) for

http://www.aoml.noaa.gov/flbay/mari95.html (4 of 9)9/10/2007 2:32:38 PM Marine Endangered Species - 1995 activity ( tail drags, digging or scraping) or the presence of eggs or hatchlings. When nests are located and their vegetation, substrate, distance from shore, dimensions (lxwxh) and salinity of adjacent waters are recorded. Hatched eggshells or hatchling crocodiles are evidence of successful nests. The number and causes of egg failure are noted whenever possible.

Growth and survival of crocodiles will be assessed by capturing and marking them during nest surveys, followed up with periodic efforts at recapturing them. Over 700 crocodiles have been marked in Everglades National Park (over 2000 in south Florida). Recapture of crocodiles tagged from previous studies will yield valuable information on long term growth and survival of crocodiles.

A salinity based habitat model was developed based on data on salinity and habitat relations of crocodiles in Everglades National Park. Overall crocodile habitat in northeastern Florida Bay was defined as the mangrove and coastal prairie fringe and offshore islands. Within this area suitability of the habitat was based on salinity levels with the most suitable habitat defined as between 0-10 ppt, intermediate suitability as 11-30 ppt, and the least suitable areas as over 30 ppt. Seasonal isohalines were obtained from monthly summaries of water quality data provided by the South Florida Water Management District.

An Everglades National Park record twenty nests were located in 1994 and new record of 21 nests were located in 1995 in an area between Cape Sable in western Florida Bay and Trout Cove in northeastern Florida Bay. Fourteen nests were successful in 1994, with raccoon predation responsible for the loss of three nests and early embryonic mortality indicated in the failure of four nests. Nine nests were successful in 1995. Nine nests were depredated by raccoons, two were lost to flooding and the cause of failure undetermined in one nest. The 1994 and 1995 nesting seasons were notable not only for the record number of nests in both years, but also in the discovery of crocodile nests on Cape Sable by Everglades National Park Ranger Lora Peppers. The last (and only) record for crocodile nesting on Cape Sable was by Willoughby in 1897.

Ninety-two hatchlings were marked in 1994 and 53 were marked in 1995. Recaptures of these animals during the 1995-96 dry season will form the basis for the assessment of growth and survival.

The following results can be interpreted from the salinity based habitat model:

1. More freshwater (lower salinity) in northeastern Florida Bay increases the amount and suitability of crocodile habitat.

2. Flows through Taylor Slough (rather than C-111) provide more and better crocodile habitat.

3. Under current conditions most suitable crocodile habitat occurs closer to C-111 drainage area than Taylor Slough.

Two predictions based on the results of this model are important.

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First, we predict that crocodiles should occur most frequently in areas with the most suitable habitat. Seventy-seven percent (n=22) of the crocodiles captured in northeastern Florida Bay during 1987-1988 were captured in an area in and around to Joe Bay. Under most hydrological conditions this area contains the most suitable habitat in proximity to known nesting areas.

The second prediction, or really recommendation, is that freshwater flows directed down Taylor Slough will have the greatest effect in improving the amount and suitability of crocodile habitat. An associated prediction is that the frequency of crocodile sightings in the Little Madeira/Mud Bay area should increase.

We hypothesize that increased freshwater flow into Florida Bay through Taylor Slough (rather than C- 111) would have beneficial effects on American crocodiles. Our analyses suggest that unless hydrological conditions are changed dramatically nesting effort and success will not be adversely affected, while the amount and suitability of habitat for crocodiles would be increased. Our habitat model predicts that Taylor Slough flows also would provide more suitable habitat in closer proximity to known nesting areas. We hypothesize that this would increase the growth and survival of hatchling crocodiles. This hypothesis can be tested by continuing to assess the relationship between growth and survival of crocodiles and hydrological conditions.

Current studies are scheduled to terminate November 1996.

Breeding Populations of Bald Eagles and Ospreys in Florida Bay

William B. Robertson, Jr. , Everglades National Park/National Biological Service; and, Oron L. Bass, Jr., Everglades National Park.

Data on the Bald Eagles (Haliaeetus leucocephalus) and Ospreys (Pandion haliaetus) inhabiting Florida Bay, initially collected because of concerns about chlorinated pesticides, may also provide insights on present ecological perturbations in the Bay. Bald Eagles and Ospreys are major avian predators in the Florida Bay system. Both have substantial populations, both nest in the winter months, and the breeding adults of both appear to be essentially resident in the Bay. Both species are predominantly fish-eaters, but Eagles, in addition, prey to lesser extent on water-birds and diamondback terrapins (Malaclemmys), and consume carrion of whatever origin when it's available.

The population database for Bald Eagles consists of annual records of nesting activity and young produced by the entire Florida Bay population. These records are derived from monthly aerial surveys of the 30 or so known nesting territories in Florida Bay (beginning in October/November) continued until the results of nesting in a given season are known with certainty. Nests are visited on the ground whenever aerial observations are ambiguous. This record of the Florida Bay population is continuous

http://www.aoml.noaa.gov/flbay/mari95.html (6 of 9)9/10/2007 2:32:38 PM Marine Endangered Species - 1995 from the nesting season of 1959-60 through that of 1994-95, except for the years 1984-85 and 1985-86 when funding failed utterly. The population database for Ospreys consists of whole-Bay air and ground counts of active nests made in eight seasons from 1968-69 to 1994-95.

Based on the above data, the breeding population and productivity of Bald Eagles in Florida Bay exhibited remarkable stability over a 32-year period of record that embraced many of the ecological extremes to which the Bay is subject. Conversely, the Bay count of active Osprey nests declined by 72.5 percent over the period of record, most of the decline apparently occurring in the 1970s. Other aspects and implications of these databases will be discussed.

Figure 1. Comparative productivity rates of primary producer components in Florida Bay. All values are the mean of at least five replicates, standard error is indicated by error bars.

Studies of Marine Turtles in Florida Bay

Barbara A. Schroeder, Blair E. Witherington, Allen M. Foley, Florida Department of Environmental Protection, Florida Marine Research Institute.

Introduction

Distribution, abundance, and seasonality of marine turtles on nesting beaches in Florida are well documented and long-term standardized surveys for nesting population monitoring are in place. In contrast, relatively little is known about the ecology and migrations of turtles in Florida waters. Information on the occurrence of marine turtles in Florida Bay is sparse. Dr. Archie Carr described Florida Bay as the center of abundance for Kemp's ridleys in the Gulf of Mexico and provided an account of the capture (for shark bait) of three species - the loggerhead, green turtle, and Kemp's ridley at Sand (Sandy) Key in 1941. Although much attention has been focused recently on the Florida Bay ecosystem, marine turtles have been essentially overlooked, despite their endangered status and their position as upper-trophic level consumers. Subsequent to Carr's account, no published accounts of marine turtles in Florida Bay can be found prior to that of Schroeder and Foley (1992) describing the initiation of marine turtle studies in Florida Bay in 1990. The Science Plan for Florida Bay recognizes living resources as a major research area and outlines six key research needs for marine turtles. In addition to the relevance of our study to the Florida Bay Science Plan, this research also responds directly to specific recommendations made by The National Research Council in their report entitled "Decline of the Sea Turtles: Causes and Preventions." The report addresses the critical need for long- term in-water studies such as this one. Likewise, the Federal Recovery Plans for the loggerhead, green turtle, Kemp's ridley, and hawksbill clearly emphasize the need for studies of developmental, foraging, and migratory habitats, all of which characterize the significance of Florida Bay to marine turtles. The primary objectives of our study are 1) to determine the species composition, population structure, sex ratio, genetic identity, and seasonal and spatial distribution of marine turtles in Florida Bay; 2) to

http://www.aoml.noaa.gov/flbay/mari95.html (7 of 9)9/10/2007 2:32:38 PM Marine Endangered Species - 1995 describe daily and seasonal activity patterns and habitat use for loggerhead and green turtles by conducting visual tracking and VHF radio, sonic, and satellite telemetry; 3) to evaluate health status of marine turtles in Florida Bay by establishing blood chemistry profiles; and 4) to describe the occurrence of fibropapilloma disease and the species composition, population structure, and spatial distribution of afflicted turtles.

Methodology

Sampling is conducted monthly from May through September and quarterly from November through April. Our primary study sites are located in the western portion of Florida Bay. Turtles are captured by several methods depending upon water clarity, tidal conditions, and type of habitat. Capture methodologies include large mesh stationary tangle nets, large mesh tangle nets drifted with the current, and hand capture by snorkelers diving from boats near turtles or swimming in the water behind turtles. Captured turtles are brought on board and measured, weighed, flipper tagged, externally examined, and photographed. Blood samples are collected from the dorsal cervical sinus and are used to determine the sex of immature turtles through radioimmunoassay, to determine genetic identities through mtDNA analysis, and to establish blood biochemical profiles as a measure of physiological status. Detailed data on number, size, and location of external tumors are collected from turtles afflicted with fibropapilloma disease. Tumor samples are collected from selected individuals. Prior to release, an individual carapace scute is spray painted with quick-dry enamel to enable in-water identification to prevent recapture by hand during the sampling period. Capture locations are determined using GPS. Environmental data collected at each capture location include water temperature, salinity, water depth, and bottom characteristics. Sightings of turtles that are not captured are recorded and geo-referenced.

To study the movements and habitat use of a subsample of turtles in Florida Bay we use VHF radio, sonic, and/or satellite transmitters. VHF radio and sonic transmitters are attached to the posterior marginals of the carapace and are designed to operate for a period of 12-18 months. Satellite transmitters are a back-pack design and are attached to the carapace using fiberglass cloth and polyester resin. The expected battery life of the satellite transmitters is 5-11 months.

Results

We captured 187 turtles between June 1990 and August 1995. The species composition is as follows: 142 (76%) loggerheads (Caretta caretta), 44 (24%) green turtles (Chelonia mydas), and one hawksbill (Eretmochelys imbricata). Seventy-nine percent of the turtles were captured by hand and 21% were captured in large-mesh tangle nets. Most turtles (68%) have been captured in Rabbit Key Basin and in the channels crossing Nine Mile Bank. Fifteen percent of our turtles were captured in Man of War Channel and Iron Pipe Channel and 5% of total captures were made in Twin Key Basin. Water clarity is a determining factor in visually searching for and hand capturing turtles and, as such, our capture locations have shifted to areas where clear water is most commonly encountered. Exploratory sampling in the Shark River area and near East and West Bahia Honda Keys has resulted in turtle sightings and some captures.

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Loggerheads ranged in size from 48.9cm to 98.7cm standard carapace length straight line (SCL), with a mean length of 80.4cm. Thirty percent of the loggerheads were males and 5% were females based on the externally observable characteristic of tail length. Because tail length may not be a reliable indicator of sex in maturing animals, we do not assign sex unless the SCL is greater than 90.0cm or the tail is clearly elongated beyond the posterior tip of the carapace, indicating a male. Of the males identified by tail length, 52% were less than 90.0cm (SCL). Green turtles ranged in size from 25.5cm to 62.9cm; no adults were captured or sighted. Mean SCL was 46.9cm. The only hawksbill captured was also immature and measured 38.2cm SCL. Sex ratios determined through radioimmunoassay will enable a calculation of the sex ratio for all life history stages represented in Florida Bay.

The prevalence of green turtle fibropapilloma disease (GTFP) in Florida Bay is alarming. Sixty percent of captured green turtles are afflicted. Of urgent concern is the 11% GTFP prevalence in loggerhead turtles, an unprecedented rate of occurrence in this species.

Our recapture rate in Florida Bay is 7%. Recapture intervals range 20 - 1,013 days. Adult male, adult female, and immature turtles have been recaptured. Loggerhead recapture locations have been in close proximity to the original capture locations. Only one green turtle has been recaptured in Florida Bay. The recapture interval was 357 days and the turtle was captured in the same fork of the same channel crossing Nine Mile Bank. We have received notification of three long-distance recaptures of turtles we tagged in Florida Bay. All three recaptures, two green turtles and one loggerhead, were captured in Cuban waters,several years after their initial capture in Florida Bay.

Three loggerheads, captured in Rabbit Key Basin, are currently outfitted with radio and sonic transmitters to facilitate the study of local movements and habitat use. Location data are collected at least once each month and all three turtles have remained in the vicinity of Rabbit Key Basin.

In collaboration with the National Marine Fisheries Service Charleston Laboratory, blood profile assessments are underway and genetic analyses will begin in early 1996. Satellite telemetry of adult male loggerheads will be initiated this winter. A long-term approach to most aspects of our research is essential due to the complex life history and longevity of these species.

Last updated: 07/16/98 by: Monika Gurnée [email protected]

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Mollusks & Crustaceans

1995 Abstracts

Pink Shrimp as Indicators of Habitat Health in Florida Bay

Joan A. Browder, NOAA, National Marine Fisheries Service, Miami, FL; Nelson M. Ehrhardt, Victor R. Restrepo, Univ. Miami Rosenstiel School of Marine & Atmospheric Science; Peter Sheridan, Z.P. Zein-Eldin, James Nance, NOAA, National Marine Fisheries Service, Galveston, TX; Cheryl Woodley, NOAA, National Marine Fisheries Service, Charleston, SC; Michael Robblee, National Biological Service, South Florida/Caribbean Field Unit, Miami, FL.

The Tortugas fishery for pink shrimp (Penaeus duorarum) experienced a severe decline in catch rates from the mid 1980s through the early 1990s. The decline appeared related to reduced recruitment, because lower catch rates coincided with decreased, rather than increased, effort, and the size distribution of the shrimp did not change. Components of the fishery have followed different time trajectories. Recruits to the fishery during the 6 months from July through December declined from 1960 through 1993, but recruits during the 6 months from January through June were more stable. This suggested there might be two cohorts in the fishery and that the decline mainly involved one cohort.

A multi-investigator study was initiated in 1994 to explore the decline in the fishery and to examine it in relation to conditions on known nursery grounds, particularly Florida Bay. The decline in pink shrimp recruitment was only one of several recent signs of deterioration in the ecological health of Florida Bay. This investigation addresses questions in the Florida Bay Interagency Science Plan concerning recruitment to coastal fisheries as related to nursery ground conditions.

Pink shrimp is viewed as a potential ecological indicator species in the adaptive environmental management process of the South Florida restoration effort. Shrimp landings are positively correlated with indices of freshwater runoff, and loss of freshwater inflow is a major hypothesis for the bay's decline. Water management actions in the early 1980s are thought to have had a major influence on freshwater flow to Florida Bay and other estuaries of Everglades National Park. In particular, after floods in August and September of 1981, regulation water stages were lowered in the South Dade Conveyance system (L-31N, L-31W, and C-111 canals). Further lowering of regulation stages took place in early 1984. This has diverted water away from Everglades National Park and Florida Bay. Pink shrimp may also act as an indicator of the health of seagrass beds. Seagrass beds have been shown to be favorable habitat for pink shrimp. A die-off of seagrass beds is one aspect of the declining ecological health of Florida Bay.

Learning more about pink shrimp ecology is the key to using this species as an ecological indicator.

http://www.aoml.noaa.gov/flbay/moll95.html (1 of 12)9/10/2007 2:32:39 PM Mollusks & Crustaceans-1995 Three critical questions helped focus study design: 1) What are the functional relationships between pink shrimp growth and survival and salinity and temperature on their nursery grounds?, 2) Where are the nursery grounds of each of the cohorts in the fishery and what time of the year are they used?, and 3) Is there more than one physiological phenotype in the fishery, responding differently to freshwater inflow?

The first question is fundamental. A positive correlative relationship between Tortugas shrimp landings, adjusted for effort, and freshwater inflow to the coast has been established by previous work of some of these investigators. For almost a decade, the National Marine Fisheries Service has used a model based on freshwater inflow indices to accurately forecast Tortugas landings. The mechanism underlying the relationship is not understood because the geographical distribution of pink shrimp suggests this species tolerates higher salinities than either of the other two penaeids in U.S. waters. Therefore, one might think that freshwater inflow would be less important to pink shrimp than to the other species.

The second question addresses another paradox. Whitewater Bay, a water body in which salinities are highly variable and seasonally brackish, was considered an example of important pink shrimp nursery habitat in studies conducted during the 1950s and 1960s. In fact, a bait shrimp fishery once operated in passes to Whitewater Bay and Lake Ingraham. Yet recent studies of pink shrimp on their nursery grounds have focused on Florida Bay and have found the highest densities in the western part, where salinities are relatively stable and approach seawater strength. Salinity is an important variable influencing physiological processes in estuarine organisms. How does the same species use nursery grounds having such different salinity regimes?

It is has been shown for some other organisms that genetic variability allows a species to conform to a wide range of conditions without necessarily requiring adaptation of the same individuals to the entire range. The third question, therefore, is: Does more than one physiological phenotype contribute to Tortugas pink shrimp landings? If so, where are the nursery grounds and what time of the year are they used? Two or more cohorts could, of course, originate from the same grounds and be exposed to different conditions because they utilize the grounds at different times of the year. But only one annual maximum in juvenile densities has been observed in western Florida Bay, which suggests that another location is a more likely nursery ground for the second cohort.

One objective of the FY94 study was to better define the within-year cohorts in the fishery and relate them back to cohorts on nursery grounds that might have contributed to the fishery. Virtual Population Analysis (VPA) was used to estimate abundance, by size and age groups, from landings data. A computer model was developed to simulate shrimp growth as a function of temperature and determine the month and day of maximum shrimp catches (e.g., Nov., April, etc.), by size, resulting from any month and day (e.g., mid June or mid Nov.) of maximum abundance of juveniles on the nursery grounds.

A second objective in the first year was to explore the full range of environmental variables that might be influencing recruitment. Exploratory analyses of archived resource survey and environmental monitoring data were undertaken to identify environmental variables statistically related to juvenile pink shrimp densities on the nursery grounds and recruitment to the fishery computed with VPAs.

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A time series of modal sea surface temperatures for the bay was developed for use in the simulation model. These data were computed from 5-day composite SST fields prepared from 4-km (to a side) resolution SST fields prepared by the University of Miami from NOAA satellite AVHRR data.

To support expansion of the simulation model to include effects of salinity, as well as temperature, laboratory experiments were conducted to measure survival and growth of young pink shrimp under different temperature and salinity combinations. Another aspect of Yr-1 work was to lay the groundwork for examining genetic variation in the pink shrimp contributing to the Tortugas fishery.

Yr-1 analyses supported our initial hypothesis that two or more major within-year age cohorts recruit to the Tortugas shrimp fishery. The analysis confirmed our cursory observation that the decrease in landings and CPUE observed from the mid 1980s through the early 1990s was due almost entirely to the decline in the fall cohort. This suggests that some change in conditions has severely affected the cohort that historically contributed most strongly to the fishery. The within-year cohorts in the fishery may come from different nursery grounds and may survive and grow best under different conditions.

Our simulation model showed that differences in growth rate during the first 30 days on the grounds resulted in substantive differences in the number of days between peak densities on the grounds and peak recruitment in the fishery. Results showed that juveniles exposed to the temperatures prevailing in the bay starting in July, in September, or in November grew at markedly different rates.

After correction of some translation errors in the historic salinity file, a strong relationship was found between Tortugas landings and salinities in Florida Bay. This result brings us closer to defining and understanding the mechanism(s) underlying the correlative relationship observed between pink shrimp landings and indices of freshwater inflow.

Yr-1 exploratory analyses of juvenile pink shrimp densities in relation to environmental variables identified significant relationships with Key West mean sea levels, wind speed, rainfall (at the Royal Palm Ranger Station), and water releases into Everglades National Park through the S-12 structures. A model based on these variables is a good estimator of the temporal pattern of juvenile densities. Rainfall and water releases through the S-12 structures are indicative of freshwater inflow to the coast.

Yr-1 laboratory experiments with pink shrimp collected from western Florida Bay indicated reduced survival at temperatures exceeding 30°C, often found in summer, and salinities of 45 ppt or greater. These salinities are common and persistent in northcentral Florida Bay basins.

Summarization of 8 yrs of remotely sensed sea surface temperature data from Florida Bay suggests that the bay had more days of temperatures greater than 30°C from 1988 through 1992 than it had from 1985 through 1987. We found that routine methods used to compute sea surface temperature from satellite imagery are inadequate for providing precise estimates of temperatures greater than 30.5°C.

Genetics work conducted during Yr-1 resulted in the design and optimization of DNA extraction

http://www.aoml.noaa.gov/flbay/moll95.html (3 of 12)9/10/2007 2:32:39 PM Mollusks & Crustaceans-1995 protocols to produce sufficient quantities of DNA for polymerase chain reaction (PCR) techniques and cloning projects. A species-specific genetic marker that distinguished pink shrimp from brown and white shrimp (Penaeus aztecus and P. setifera) was identified in mtDNA. Preliminary analyses have been conducted to detect mtDNA regions of variability that might be useful in addressing population level questions in pink shrimp. Simultaneously with the mtDNA work, we started preparing a "shotgun" genomic library to screen for microsatellites, which have been powerful population-level markers in marine mammals and teleosts.

Our Yr-1 work showed, for the first time, a correlation of juvenile densities with freshwater inflow. Previous work had suggested an effect of freshwater inflow on landings, but this new analyses suggests an effect of freshwater inflow on early survival, as reflected in juvenile densities on the nursery grounds. Also for the first time, a significant relationship was found between Tortugas landings and salinities in Florida Bay. This helps to support a causal relationship in the correlation of landings with indices of freshwater inflow.

Our laboratory results concerning tolerances to temperature and salinity suggest that parts of Florida Bay may be excluded as pink shrimp nursery grounds in most years. Temperatures greater than 30°C often are found in Florida Bay in the summer, and salinities greater than 45 ppt are persistent in some parts of Florida Bay through all but the wettest years.

Another significant Yr-1 finding is the suggested linkage of densities with oceanic water levels and, through wind stress, Ekman transport. Both might relate to transport processes carrying pink shrimp from their offshore spawning grounds to their inshore nursery grounds. The explanatory strength of these variables suggest that we should determine whether substantive changes in oceanic patterns occurred within the period from the mid 1980s to the early 1990s that could have affect larval transport.

On the other hand, the relationship with sea level may reflect some seasonal or long term influence of sea level on shrimp habitat. Juvenile shrimp appear to occur at highest densities on banks and flats. These areas are, to varying degrees, either exposed or subjected to extremely shallow water during lower stages of the tide; and the mean tide varies seasonally, causing the sea level at low tide to be lower during some times of the year. These sea level variations may affect shrimp growth and survival.

Although shrimp landings were extremely low from about July, 1986-June, 1987, through July, 1992- June, 1993, they increased greatly in 1993-1994 and 1994-1995. The increase corresponds to the higher rainfall of the last few years, appearing to further confirm a causal relationship between catch rates and freshwater inputs. This supports the focus of our Yr-2 work.

Recently, we initiated a field study to compare pink shrimp densities in Whitewater Bay with densities being measured in western Florida Bay in a related project. The same gear and procedures will be used. This will be the first time that the throw trap, a more efficient gear than that used previously in Whitewater Bay, will be used concurrently in both western Florida Bay and Whitewater Bay.

http://www.aoml.noaa.gov/flbay/moll95.html (4 of 12)9/10/2007 2:32:39 PM Mollusks & Crustaceans-1995 Critical questions our continuing research addresses are: 1) What nursery grounds provided the main support for the fishery before its productive value declined?, 2) What nursery ground supported the fishery during the 9-yr period of exceptionally low catches, 3) Which environmental variables are most important in determining pink shrimp recruitment, and 4) What are the mechanisms for their effects? The fact that catch rates in the fishery have improved in the last two years may help us answer these questions.

The Effect of Changing Juvenile Habitat on Spiny Lobster Recruitment

Herrnkind, William F., Florida State University, Tallahassee, FL 32306; Mark Butler J. IV, Old Dominion University, Norfolk, VA 23529; John H. Hunt , Florida Department of Environmental Protection, Florida Marine Research Institute, Marathon, FL 33050. .

Florida Bay and the shallow waters surrounding the Florida Keys are the primary Florida nursery for the Caribbean spiny lobster (Panulirus argus). However, environmental conditions are deteriorating in the Florida Keys and a cascade of ecological disturbances have recently plagued the region, thus revealing the coupled dynamics of this tropical marine ecosystem. Our studies of spiny lobster recruitment, set against this backdrop of environmental change, demonstrate how changes in the coastal environment can affect key fishery species, sometimes in unexpected ways. For example, salinity, temperature, and nutrient loads have increased in portions of Florida Bay. Changes in water quality have presumably contributed to the loss of thousands of hectares of seagrass in Florida Bay, and together have sparked the development of cyanobacteria blooms that have become widespread in the bay since 1991. An unexpected consequence of the cyanobacteria blooms was the decimation of the sponge community throughout much of central Florida Bay. The ramifications of these environmental changes for the lobster population in south Florida are complex. Hardbottom habitat replete with macroalgae, sponges, solution holes and other structures are thought to be prime nursery habitat for lobsters, but recent results suggest that seagrass may be more important in this regard than we previously thought. Although the implications of seagrass loss for lobster recruitment might therefore seem obvious, the actual repercussions are probably minimal because the areas impacted thus far are largely isolated from postlarval supply or have salinity and temperature regimes that are intolerable to settling postlarvae. In fact, abnormal salinity or temperature in much of northeastern Florida Bay diminish the recruitment potential of lobsters. The most serious threat to lobster recruitment to date is the widespread mortality of sponges. Juvenile spiny lobsters rely on sponges for shelter, so the rapid loss of sponges at sites exposed to cyanobacteria blooms has resulted in similar declines in local lobster abundance and shifts in shelter use by the remaining individuals. We recently began investigating the ramifications of ecosystem change, particularly the loss of sponges, on lobster recruitment on a regional scale by coupling large- scale surveys with a spatially explicit, individual-based model of the system. The initial predictions from the model are that lobster recruitment will decline 2 - 19%, depending on the availability of alternative shelters, which corresponds with a field survey based estimate of a 10% loss in new recruits.

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Mapping Florida Bay Benthic Assemblages: Using Mollusks to Assess Faunal Change

William G. Lyons, Florida Department of Environmental Protection, Florida Marine Research Institute.

Objectives: Acquire information on the composition of faunal assemblages and map their distributions in Florida Bay, using mollusks as indicator organisms.

Mollusks are important components of the Florida Bay fauna. More than 200 species of mollusks live in brackish, estuarine, and marine waters of Florida Bay (Tabb and Manning, 1961; Tabb et al., 1962; Turney & Perkins, 1972), and their shells in bay sediments constitute more than 75% of all particles whose sizes exceed 1/8 mm (125 microns) (Ginsburg, 1972), prompting Turney (1972:15) to declare the fauna of the bay to be dominantly molluscan. The concept of Florida Bay "sub-environments" used today was promulgated on evidence from distributions of dead (empty) mollusk shells (Turney, 1972; Turney & Perkins, 1972). This report documents assemblages of live mollusks in the bay during summer 1994 and compares their distributions to the sub-environments described from dead shells several decades ago. Results will provide a baseline for measuring changes due to environmental perturbation or to efforts to mitigate such disturbance.

Methods: To avoid potential biases of a priori stratification, the initial search for distributional pattern applied equal sampling effort throughout the bay using an iteration of the U.S. Environmental Protection Agency hexagonal grid (White et al., 1992) that subdivided the study area into approximately 300 units (area of each unit 6 km2). By choosing every third unit, a sampling pattern was obtained that covered the bay evenly with 101 noncontiguous units. Global positioning system (GPS) technology was used to locate units and to identify sampling sites, which were selected within the prevalent environment of each unit. Water temperature, salinity, conductivity, pH, and dissolved oxygen were measured at each site; surface and bottom values were recorded when depths exceeded 1 m. Bottom sediments (mud, clay, sand, peat, etc.) and vegetation were also noted.

Fifteen 6-inch (15.24-cm) diameter cores were taken at each site. Cores were washed through two sieves (mesh sizes 3 mm [upper] and 1 mm [lower]), and sieved residues of three consecutive cores were combined to produce five samples of each size fraction at each site. A core sampled a surface area of 183 cm2 (0.018 m2); surface area of samples combined from three cores was 0.054 m2, and five three- core samples represented an area of 0.27 m2.

Large-fraction (>3-mm) samples were sorted into five categories (mollusks; annelid worms; arthropods; echinoderms; other phyla); 10% of the samples were re-sorted to ascertain rates of error. Sample residue, principally empty shells, was air-dried and stored for use in other comparisons. Live-collected mollusks were identified to the lowest taxonomic unit (usually species) and counted. Resultant data sets were analyzed using the Community Analysis System (CAS) program. Coefficients of intersite similarity [abundance data transformed, logn (x+1)] were used to identify faunistically similar groups

http://www.aoml.noaa.gov/flbay/moll95.html (6 of 12)9/10/2007 2:32:39 PM Mollusks & Crustaceans-1995 (assemblages) whose distributions were mapped using GIS techniques.

Results: Sampling in 1994 was conducted during 1-23 June (71 sites); 7-14 July (2 sites); 3-17 August (28 sites); and 31 August (2 sites resampled; original samples poorly preserved). Fifteen cores were taken at each of 101 sites (total cores 1515) and combined in sets of three (1515/3 = 505 samples). Surface area sampled at each site was 0.27 m2; total surface area sampled was 27.27 m2.

Salinity ranged from <10 ppt. in Joe Bay to 50-52 ppt. at three sites near Rankin Key. Sites where salinity exceeded 40 ppt. were common in the central bay. Salinities in the eastern bay were markedly lower (31-35 ppt), even in early and middle June before the full onset of summer rains.

Live-collected mollusks consisted of 94 species, 1,436 species lots and 13,774 specimens. Numbers of species at sites ranged from 1 to 23 (mean = 7.3), but 4 to 9 species were taken at nearly two-thirds (63%) of the sites. Sites with higher species richness (>9 species) generally were located west of a line extending from Flamingo to Lignumvitae Key, but high species richness also occurred at Buttonwood Sound, Blackwater Sound, and at several sites along the north of the more easterly Florida Keys. Sites with fewest (1-3) species were usually located in the upper bay near and east of Rankin Key or in basins of the eastern bay.

Molluscan abundance varied greatly among the sites; numbers of specimens per site ranged from 1 to 6406, and maximum density was more than 23,700/m2. Five sites where density exceeded 1,000 mollusks/m2 were dominated by a mussel, Brachidontes exustus. Those sites tended to have below- average species richness (<7) but also included the site of highest species richness, Pontoon Bank. Mussels occurred in low density (<200/m2) at most sites in the eastern half of the bay, but the species displayed great increases in density (1,000-23,725/m2) at several sites along a track extending from western Madeira Bay southwestward through Whipray Basin and Twin Key Basin to Pontoon Bank. This species was virtually absent from the northwestern part of the bay; a single juvenile was found at 1 of 29 sites north and west of Pontoon Bank.

Most species occurred in zones of semi-contiguous distribution, indicating affinity for particular subenvironments. Coefficients of intersite similarity indicate a Gulf group (7 sites; 33 species), a Lake group (2 sites; 3 species), and a Bay group (92 sites). The Bay group includes an Eastern component (45 species; 29 sites), a Central component (35 species; 18 sites), a Western component (57 species; 33 sites, with a southern and two northern subgroups), and 15 sites either transitional between larger components or too depauperate to classify. The Central component generally tracked the distribution of highest salinity and the path of concurrent blooms of microalgae. Most Central sites were species-poor but several were specimen-rich, reflecting the high densities of Brachidontes exustus.

Site groupings of assemblages of live mollusks in 1994 generally confirmed the locations of the Interior, Transitional and Gulf sub-environments proposed by Turney & Perkins (1972), but the Northern and Atlantic sub-environments they defined were not distinguished from other groupings in 1994, probably because of the influence of widespread hypersalinity.

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Continuation of Work: Thirty sites, proportionally allocated among 7 groups and subgroups of 1994, were resampled in August 1995 to test consistency of groupings. Salinity was measured again at all 101 sites for comparison with 1994 values. Fifteen of the sites will be resampled several more times during the year to ascertain the influence of seasonal variation in species abundance on site groupings perceived in summer mapping efforts.

References:

Ginsburg, R. N. 1972. Introduction to Recent sedimentation. Pp. 4-11 in R. N. Ginsburg, ed. South Florida carbonate sediments. Sedimenta II. University of Miami, Fisher Island Station, Miami Beach, Florida.

Tabb, D. C., D. L. Dubrow, and R. B. Manning. 1962. The ecology of northern Florida Bay and adjacent estuaries. State of Florida Board of Conservation, Technical Series No. 39:1-79.

Tabb, D. C., and R. B. Manning. 1961. A check list of the flora and fauna of northern Florida Bay and adjacent brackish waters of the Florida mainland collected during the period July 1957 through September 1960. Bulletin of Marine Science of the Gulf and Caribbean 11(4):552-649.

Turney, W. J. 1972. [Florida Bay] Molluscan fauna. Pp. 14-16 in R. N. Ginsburg, ed. South Florida carbonate sediments. Sedimenta II. University of Miami, Fisher Island Station, Miami Beach, Florida.

Turney, W. J., and B. F. Perkins. 1972. Molluscan distribution in Florida Bay. Sedimenta III. University of Miami, Fisher Island Station, Miami Beach, Florida. 37 pp.

White, D., A. J. Kimmerling, and W. S. Overton. 1992. Cartographic and geometric components of a global sampling design for environmental monitoring. Cartogr. Geograph. Inf. Syst. 19(1):5-22.

Temporal and Spatial Variation in Seagrass Associated Fish and Invertebrates in Western Florida Bay: A Decadel Comparison

Michael B. Robblee, National Biological Service, South Florida/Caribbean Field Laboratory, Florida International University, Miami, FL.

In the fall of 1987, a widespread, rapid die-off of turtle grass, Thalassia testudinum, began in Florida Bay. Die-off occurred in areas of dense seagrass cover and principally in and around Rankin Lake, Rabbit Key Basin and Johnson Key Basin in western Florida Bay. Increasingly extensive and persistent turbidity and algal blooms, apparently linked to the loss of seagrass cover, have been associated with active seagrass die-off sites since 1988 and have characterized western and central Florida Bay since

http://www.aoml.noaa.gov/flbay/moll95.html (8 of 12)9/10/2007 2:32:39 PM Mollusks & Crustaceans-1995 1991. Recolonization of impacted grass bed habitats by shoal grass, Halodule wrightii, is occurring.

Loss of seagrass habitat on the scale observed in Florida Bay is unprecedented in tropical seagrass systems and hypothesized to threaten the Bay's water quality, sportfishery, and nursery function. In the short-term, grass canopy loss and declining environmental conditions may lead to shifts in species composition and reduced abundance of grass canopy dependent organisms. Over the long-term increasing seagrass habitat heterogeneity may lead to enhanced nursery function and an improve sportfishery.

A detailed quantitative database is available from Johnson Key Basin from October 1984 to April 1987 prior to seagrass die-off. Limited additional data is available from between May 1989 and August 1991, a period following the onset of seagrass die-off in the Bay but prior to the extensive and persistent plankton blooms which have characterized it since 1991. For caridean shrimps, fishes and pink shrimp this database documents population and community dynamics and spatial relationships with seagrass habitat. Therefore, it provides an excellent baseline against which to observe the response of characteristic seagrass associated species in Florida Bay to grass canopy loss, seagrass community change, and changing environmental conditions following seagrass die-off. The purpose of this project is to duplicate over the period, October 1994 to April 1997, the experimental design and sampling protocols employed previously in Johnson Key Basin prior to seagrass die-off in order to address the following objectives: 1) to document changes in seagrass community structure and habitat complexity following seagrass die-off; 2) to document changes in species composition, abundance, and seasonality of caridean shrimps and fishes with changes in seagrass habitat; 3) to document temporal and spatial abundance and size frequency distribution of the pink shrimp, Penaeus duorarum, in relation to changes in seagrass habitat; and 4) to evaluate quantitative relationships between animal abundance and species composition and grass bed micro-structure and habitat complexity.

In 1984 thirty stations were established in Johnson Key Basin. Stations were located generally with no a priori consideration of the seagrass habitat present. The stations were evenly stratified among the principal seagrass macro-habitat types present in Florida Bay: bank, basin, and near-key. Nine of these thirty stations, 3 within each macro-habitat type, were repetitively sampled on a six-week interval between October 1984 and April 1987 in order to address questions of timing. These nine stations were also sampled between August and December on a six-week interval between 1989 and 1991. All thirty stations were sampled four times (January 1985, May 1985, May 1989, and January 1990) in order to address animal versus habitat questions.

Quantitative animal samples were collected using a throw trap. The throw trap consisted of an open­ ended 1 m2 aluminum box, 45 cm deep, with panels of nylon netting (0.16 mm stretch mesh DELTA netting) attached on parallel edges at the top of the throw trap. Each panel of netting was large enough to cover the top of the throw trap when it was used in water deeper than 45 cm. At each station four replicate throw trap samples were located along a 20 m transect, one each in each 5 m segment. After the trap was dropped in place, it was cleared of animals with three separate passes of a 1 m wide frame sweep net of mesh size similar to the panels. It has been estimated that three sweeps collect at least 95% of target species present in the trap. SCUBA was used while clearing the trap in deep water. All fishes,

http://www.aoml.noaa.gov/flbay/moll95.html (9 of 12)9/10/2007 2:32:39 PM Mollusks & Crustaceans-1995 caridean and penaeid shrimps were removed from each throw trap, identified, counted and sized as appropriate in the laboratory. When all thirty stations were sampled the connection between these seagrass associated animals and grass bed structure was made by associating each throw trap collection with estimates of grass bed micro-structure including: seagrass standing crop and blade density; algal biomass; sediment texture, depth, organic content and compaction; root and rhizome biomass; and water depth.

During the current effort six-week interval sampling has been ongoing since October 1994 (9 collections have been made) and the thirty stations have been sampled in January and May 1995. Dr. Mike Marshall of Mote Marine Laboratory is processing samples and identifying the organisms recovered. To date processing efforts have emphasized back-logged samples originally collected between 1989 and 1990 and recent samples collected during January and February 1990. Results reported here focus on a comparison among the thirty stations sampled in January/February of 1985, 1990 and 1995.

Not all of the thirty stations were sampled in each of the three years. Extreme low water in Florida Bay characteristic of January and February precluded sampling high bank stations successfully in all three years. Because of this results reported here are based on the twenty-four stations (5 bank, 9 basin and 10 near-key) sampled in each year. At these sites distinct changes in seagrass habitat have occurred since 1985. By 1995 the standing crop of Thalassia had declined by 82% as compared to 1995. Similarly, Halodule had declined by 53% and Syringodium has completely disappeared. These changes resulted in a marked shift in seagrass dominance among the 24 stations. In 1985 Thalassia was the dominant grass at 17 of 24 stations in Johnson Key Basin; Halodule dominated at 5 stations, all of them near-key habitats. By 1995 Thalassia dominated at only 9 stations while Halodule had expanded its presence into deeper water and dominate at 11 of 24 stations. Further, by 1995 Syringodium, never common, had disappeared and a new habitat, bare sediment, not present in 1985, dominated at 4 stations.

The abundance of seagrass associated caridean shrimps, fishes and pink shrimp was lower in 1995 when compared to either 1985 or 1990. Habitat change due to seagrass die-off in 1990 was localized within Johnson Key Basin and apparently affected only 6 of the 24 stations unlike 1995 when all but 6 stations evidence significant habitat change. Species composition differences were evident in 1995 when compared to 1985 and 1990. The killifishes, Lucania parva, and Floridichthys carpio, and the toadfish, Opsanus beta, were present in significantly lower numbers than in previous years. In contrast, the code goby, Gobiosoma robustum, and the bay anchovy, Anchoa mitchelli were found in greater numbers. The killifishes were community dominants within the Johnson Key Basin grass bed prior to widespread habitat change and virtually absent in 1995. Among the caridean shrimps, Alpheus sp. have increased in abundance, however, this result may be a sampling artifact due to the loss of the grass canopy. Evidence was not found supporting the hypothesis that increasing coverage by Halodule would translate to increasing recruitment of the pink shrimp, Penaeus duorarum.

At this point the project will continue with six-week interval sampling through April 1997. On completion, effects of seagrass die-off on seasonal timing can be addressed in addition to animal/habitat relationships. Additionally, data collected in this project will continue to contribute to ongoing statistical and population dynamics models of the pink shrimp in relation to the Tortugas fishery and to the

http://www.aoml.noaa.gov/flbay/moll95.html (10 of 12)9/10/2007 2:32:39 PM Mollusks & Crustaceans-1995 expansion of the ATLSS fish and invertebrate model into Florida Bay.

Sponge Biomass Estimates in the Upper and Middle Keys, With Reference to the Impact of Extensive Sponge Mortalities

John M. Stevely, Florida Sea Grant Extension Program, 1303 17th St. W., Palmetto, FL 34221-2998, (941) 722-4524, fax (941) 742-5998; Donald E. Sweat, Florida Sea Grant Extension Program, 36702 Highway 52, Dade City, FL 33525-5198, (904) 521-4288, fax (904) 523-1921.

The work described here was initiated in response to concerns regarding ecological and fishery impacts resulting from increased sponge harvesting effort in the late 1980s and early 1990s. The objective of the initial phase of the work was to document and quantify the contribution of commercial sponges (sponges of the genera Hippospongia and Spongia) to total sponge community biomass.

During 1991 and 1992 a total of 15 areas were sampled (five areas north of Long Key, four areas within Everglades National park, two areas west of Everglades National Park and four areas north of Marathon). The total area surveyed was 34,620 m2. Sampling methodology consisted of counting all sponges found within sixteen 100-m x 2-m transects at each area. During this phase of the study specific numerical abundance was recorded only for commercial species (Hippospongia lachne, Spongia barbara, Spongia graminea) and largest most common species (Spheciospongia vesparia, Ircinia campana, Ircinia strobilina, and Ircinia spp.). All other sponges were lumped into a miscellaneous unidentified category. In addition to numerical counts, data on volumetric biomass of the different sponge species and sampling categories were collected. This methodology consisted of estimating sponge specimen volume by measuring the volume of water displaced when the sponge was placed in a bucket fitted with an overflow spout.

The mean abundance for all sponges was 7,250/hectare and for commercial sponges was 106/hectare. The mean volumetric biomass of all sponges was 364 ml/m2. These data represent the most compressive baseline information available on sponge community biomass in portions of the area subsequently affected by sponge mortalities. All methods employed to estimate sponge biomass indicated that the contribution of commercial sponge biomass to the total sponge community biomass was relatively small (1.4% based on numerical counts, 2.4% based on volumetric estimates). Two species of sponges Spheciospongia vesparia (loggerhead sponge) and Ircinia campana (vase sponge) represented 68% of the total sponge community biomass based on volumetric estimates.

The effects of sponge mortalities, apparently caused by cyanobacterial blooms, became apparent in late 1992. Consequently, a second phase of work was begun to focus on documenting the effects of the sponge mortalities on sponge populations and monitoring the recovery or lack of recovery of sponge populations in following years. Fiscal and time constraints limited follow-up work to two areas (one off of Long Key and one of off Marathon) in 1993 and 1994, In 1995 a third area in Everglades National

http://www.aoml.noaa.gov/flbay/moll95.html (11 of 12)9/10/2007 2:32:39 PM Mollusks & Crustaceans-1995 Park (west of Arsenicker Keys) was added to the sampling regime.

Results of the 1993 field work documented highly significant declines in sponge abundance, with a reduction of up to 90% of the sponge community volumetric biomass. Based on sampling data and general field reconnaissance, the severity of the mortality varied significantly over the entire area affected by the cyanobacterial blooms. Data indicated that the sponge Cinachyra sp. was the most resistent to the sponge mortalities; sponges of the genera Spongia, Hippospongia and Ircinia appeared to be among the most susceptible.

The loggerhead sponge (Spheciospongia vesparia) appeared to more resistent than many species, but was completely eliminated throughout extensive areas.

As work progressed in 1994 and 1995 we began to develop a more comprehensive listing of the species previously lumped in the miscellaneous unidentified category. The most recent work now includes counting 20 sponge species. Therefore, if future work is funded, a much more complete analysis of sponge communities in the sampling areas will be possible. Analysis of the 1994 and 1995 data has not yet been completed. A preliminary perusal of the data indicates some initial evidence of recovery in the Marathon area, and possibly increased abundance of some sponge species compared to pre-mortality conditions. Due to the manner in which of the data were collected in 1991 and 1992 it may not be possible to conclusively document which species are proving to be the most rapid recolonizers. Data collected at the third monitoring area in Everglades National Park, beginning in 1995, provides a dramatic contrast with the other two areas sampled in 1993 and 1994. Data from this area indicates an even more dramatic impact, and may suggest the area has been subjected to additional mortality events.

The work conducted to date has been supported by the Florida Department of Environmental Regulation Florida Marine Research Institute, Florida Sea Grant College Program, and Keys National Marine Sanctuary Program. The 1995 work was conducted in collaboration with Dr. Shirley Pomponi, Harbor Branch Oceanographic Institution, and the FDEP contract supporting this work will be completed by November, 1995.

Currently, no funding has been obtained for future work. It is abundantly clear that many years will be required for sponge populations to recover to pre-mortality conditions. Therefore, future long term funding is needed to continue and build upon the work that has been accomplished. Without such a long term commitment to document the recovery of sponge populations, efforts to assess alterations of hardbottom communities, monitor ecological conditions, and model Florida Bay food webs will be severely hampered.

Last updated: 07/16/98 by: Monika Gurnée [email protected]

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Salinity & Nutrients

1995 Abstracts

Sediments, Episodic Land Runoff, and Localized Epicodic Groundwater Flushing as Nutrient Sources to South Florida Coastal Waters

Larry Brand , Professor, Division of Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Cswy, Miami, FL 33149 (305) 361­ 4138, FAX (305)361­4600, Email: [email protected]; Alina Szmant, Associate Professor, Division of Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Cswy, Miami, FL 33149 (305) 361­4138, FAX (305)361­ 4600, Email: [email protected] .

I have two projects that will be beginning in the fall of 1995. NOAA is funding a research project (Project 1) by Alina Szmant and me to examine sediment­water column interactions in nutrient­ microalgal dynamics in Florida Bay and the Florida Keys National Marine Sanctuary. EPA is funding me (Project 2) to search for and document ephemeral nutrient inputs into coastal waters around the Florida Keys from surface runoff and localized episodic groundwater flushing resulting from large rainstorms.

Project 1

Although it is the extensive phytoplankton bloom that is of present concern, one cannot study plankton and water column nutrients in isolation from the sediments in shallow water embayments such as Florida Bay. Diffusion, resuspension, irrigation by macrobenthic animals, macrophyte translocation and diel migration between the water column and the sediments by dinoflagellates and other phytoplankton can result in significant transfer of nutrients from the sediments to the water column. Whatever the ultimate source of the nutrients that are now generating the phytoplankton blooms in Florida Bay (dead sea grasses, human activities in peninsular Florida or the Florida Keys), it is likely that most of the nutrients within the system reside in the sediments, not the water column. A large pool of nutrients in the sediments could generate phytoplankton blooms for a long time after the ultimate nutrient source is cut off. Any restoration effort must take into consideration the benthic nutrient pool.

Although the data are somewhat sparse, a number of studies in shallow waters have found more microalgal biomass in the surface sediments than in the water column. To understand microalgal dynamics in the water column, we need to also understand microalgal dynamics in the sediments and the coupling of the two. Is it one microalgal community that occupies both the water column and benthic

http://www.aoml.noaa.gov/flbay/sali95.html (1 of 21)9/10/2007 2:32:40 PM Salinity & Nutrients-1995 habitat or two distinct microalgal communities, one in the water column and one in the sediment surface, which occasionally get mixed together during resuspension events? Do the microalgal biomasses in the water column and sediments increase and decrease over time and space together, or does an increase in one cause a decrease in the other?

Our overall goal is to determine the extent to which processes in the sediments affect the supply of nutrients and phytoplankton to the water column of Florida Bay, examine some of the mechanisms by which this occurs, and examine how important these may be in enhancing transport of nutrients into the Florida Keys National Marine Sanctuary and its reefs. Although other potential mechanisms such as macrophyte translocation may exist, we will focus on the importance of resuspension of the sediments, diffusion, and diel vertical migration of microalgae between the sediments and the water column as mechanisms for transporting benthic nutrients to the water column.

The degree of coupling between nutrients and microalgae of the sediments and water column is important to the way in which nutrients from Florida Bay may ultimately reach the FKNMS reefs. In addition to hydrographic transport of dissolved nutrients in the water column from Florida Bay to the reefs, one must consider the hydrographic transport of planktonic biomass and resuspended sediments.

The basic core of this research will be to sample 10 diverse sites in Florida Bay and 7 sites along a V­ shaped transect from the Long Key Viaduct E and S to the reefs. The exact locations may change as we coordinate our research with that of others working in Florida Bay. The main purpose of the stations in Florida Bay is to examine the relationships among nutrients and microalgae in the sediments and water column. The selected stations include basins which we expect to differ in these variables. The transect from the Long Key Viaduct will be used to examine the transport of the different forms of nutrients from Florida Bay to the reefs.

Each of the stations will be sampled every 3 months to get an estimate of variability on a seasonal time scale. At least twice a year, each of the stations will also be sampled 4 times during a 2 week time series after a major storm event to examine the magnitude and persistence of resuspension and its effects on water column nutrients and microalgae and their transport to the reefs. Our goal is to sample after a winter storm with winds primarily from the NW and after a tropical storm from the SE in the summer.

The goal of the overall sampling regime is to examine the pelagic­benthic partitioning of nutrients and microalgae under a diversity of environmental conditions. Although more frequent sampling is always desirable, quarterly sampling along with two storm event time sequences each year at 17 stations should provide us with a wide range of environmental situations to analyze and compare, which is our primary objective. Budget constraints preclude more frequent sampling.

At each station we will measure 3 replicate water samples for ammonium, nitrate, phosphate, chlorophyll, turbidity, particulate dry weight, and particulate nitrogen and phosphorus. Also at each station 3 replicate sediment cores will be taken for the measurements of benthic chlorophyll; porewater ammonium, nitrate and phosphate; extractable (sorbed) inorganic nitrogen and phosphorus; total

http://www.aoml.noaa.gov/flbay/sali95.html (2 of 21)9/10/2007 2:32:40 PM Salinity & Nutrients-1995 nitrogen and phosphorus; porosity; and particle size distribution. Sorbed nutrients constitute a reservoir of inorganic nutrients that are in equilibrium with porewater nutrients. As porewater nutrients are utilized by benthic plants and algae, sorbed nutrients can be released into the porewaters. Further, sorbed nutrients may be a source of enrichment to the water column during resuspension events. Population abundance of selected species of microalgae (species that can be easily identified by light microscopy) will be estimated in both the water column and the sediments. We plan to compare chlorophyll concentrations to turbidity and suspended particulates along with individual microalgal species distributions to estimate degree of resuspension.

Once a year at 5 of the Florida Bay stations, 48­hour diel studies will be conducted on the vertical distribution of microalgae in the water column and sediment (both total chlorophyll and selected individual species) and the vertical distribution of nutrients in the sediments. At the same time, benthic chambers will be used to measure the actual diffusional flux of nutrients out of the sediments, with emphasis on seagrass depauperate areas.

One or two species of dinoflagellates that undergo diel vertical migration in Florida Bay will be isolated into culture and their behavior studied in laboratory microcosms. The microcosms will have a water column over ca. 10 cm of sediment, with different concentrations and combinations of nitrogen and phosphorus in the water column and sediment porewaters as independent variables. This will allow us to examine how diel vertical migration behavior changes with different nutrient regimes under controlled experimental conditions and better interpret our field data from Florida Bay.

Project 2

It is generally agreed that ecological changes are occurring in the FKNMS. One of the suspected causes of some of these changes, increased nutrients, is well known to alter ecosystems. For example, increased nutrients can cause macroalgae to overgrow corals. It has been estimated that there are 25,000 cesspools and septic tanks, 281 injection wells, 4 active and 10 inactive landfills, 182 marinas with 2707 wet slips, and 1410 live­aboard boats in the Florida Keys. These sources along with several sewage outfalls, high nutrient water in Florida Bay, and other human activities are thought to be injecting nutrients into FKNMS waters, but in most cases are not yet proven to be significant. Because in many cases the injection of nutrients is ephemeral or highly local, an extremely intense sampling program in both space and time is needed to detect many of these inputs. To date, such intensive data have not been collected because of the expense. Part of the reason for this is the relatively large number of parameters that are usually measured, which drives up the cost per station.

Spatially intensive sampling is needed to pinpoint local sources of nutrients. Not only point sources such as canals, outfalls, and marinas, but even groundwater may seep out in localized areas because of structural faults and solution holes in the limestone. Because much of the nutrients can be expected to come from surface runoff and groundwater flow driven by rainstorms, sampling needs to be designed around weather events and not just at random. A buildup of nutrients in groundwater of the Florida Keys during the dry season and an increase in nutrients in local marine waters during the wet season has been

http://www.aoml.noaa.gov/flbay/sali95.html (3 of 21)9/10/2007 2:32:40 PM Salinity & Nutrients-1995 observed, suggesting that rainfall drives nutrient rich groundwater into local marine waters. The highest concentrations of chlorophyll in Biscayne Bay occur right after the first large rainfall at the end of the dry season, again suggesting rain driven flushing of nutrient rich groundwater or surface runoff. Also supporting this hypothesis was the finding of a strong negative correlation between chlorophyll and salinity, indicating that most nutrients in Biscayne Bay are associated with freshwater flow from land. It has recently been shown that nutrients from sewage injected into the Keys groundwater can make its way into coastal waters rather quickly. In conclusion, frequent and spatially intense sampling is needed to detect many of the fluxes of nutrients into FKNMS waters.

The basic objective is to detect nutrient inputs that may be highly localized or ephemeral. To do this, we need to measure a large number of samples. This will be done by using a rapid, inexpensive method of detecting nutrient eutrophication that can be carried out within a reasonable budget. The method is based on the fact that most nutrients are quickly taken up by plants in shallow tropical waters and phytoplankton increase their biomass quickly in response to nutrients, so that the measurement of chlorophyll as an indicator of plant biomass is a better and more sensitive indicator of nutrient eutrophication than is the measurement of the residual nutrients. The primary method to be used is based upon the fact that in vivo chlorophyll fluorescence is directly proportional to total chlorophyll concentration when the photosynthetic electron transport system is blocked with 3­(3,4­dichlorophenyl)­ 1,1­dimethylurea (DCMU). The fact that DCMU enhanced chlorophyll fluorescence can be measured much more quickly than can standard extracted chlorophyll concentration or nutrient concentration means that we can greatly reduce cost per sample and therefore greatly increase sample size in space and time with a limited budget.

The primary task will be to collect water samples at 200 stations on three different days following large rainstorms to determine the spatial distribution of chlorophyll and identify localized sources of nutrient eutrophication resulting from rain driven surface runoff or groundwater seepage. All 200 stations will be sampled over a 2 day period using a high speed boat. Half of the stations will be sampled on days 1, 3, and 5 after each rainstorm and the other half will be sampled on days 2, 4, and 6.

At each station, determined with a GPS instrument, 500 ml of water will be taken at a depth of 0.5 meters and temperature, salinity and oxygen will be measured with a Hydrolab system. In vivo chlorophyll fluorescence will be measured with a Turner Designs 10­000R fluorometer, 10­5 M DCMU will be added and fluorescence once again measured. 100 ml of water will be preserved with 5% formalin buffered with sodium tetraborate and another 100 ml will be frozen so that other analyses can be conducted in the future. At 10% of the stations, 3 replicate water samples will be taken, and in addition to measuring DCMU enhanced chlorophyll fluorescence, 100 ml of water from each replicate will be filtered (after adding 1 mg of MgCO3 ) through GF/F glass fiber filters and the filters will be frozen. These filters will be extracted for 30 minutes with 10 ml of dimethyl sulfoxide and then with an added 10 ml of 90% acetone at 5°C overnight and measured fluorometrically before and after acidification for the measurement of chlorophyll and phaeopigment concentrations. The replicates at these stations will be used to assess the accuracy of our methods and to examine the relationship between extracted chlorophyll concentrations and DCMU enhanced chlorophyll fluorescence.

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Nutrient Exchange Between Florida Bay and the Everglades' Salinity Transition Zone:the Importance of Transformations in Mangrove Wetlands

Daniel L. Childers, Southeast Environmental Research Program & Department of Biological Sciences, Florida International University, Miami, FL 33199; John W. Day, Jr. , Enrique Reyes, Center for Coastal, Energy, and Environmental Resources, Louisiana State University, Baton Rouge, LA 70803; David Rudnick, Everglades Systems Research Division, South Florida Water Management District, West Palm Beach, FL 33416.

Background and Introduction:

In 1987, large areas of Thalassia beds began to die off in Florida Bay--a phenomenon that continues today. As a result of this major event, and the secondary ecological effects that have come to be related to it, Florida Bay has become a focus of both research and management energies. The cause or causes of these major changes remain unresolved. It appears clear, however, that the greatly modified hydrologic regime of the greater Everglades watershed has had an effect on the Florida Bay estuary. This modified hydrologic regime has caused a virtual elimination of the freshwater inputs to the estuary. During the summers of 1988 and 1989, salinities in central Florida Bay exceeded 60‰ and temperatures exceeded 40°C. The Everglades Forever Act mandated that more freshwater be directed to flow into the Florida Bay estuary and that the distribution of this flow be as close to historical patterns as possible. It is important that we understand how these changes in the quantity, timing, and [potentially the] quality of this water delivery will affect the Florida Bay estuary. In this study, we are focusing on the mangrove transition zone separating the Bay from the freshwater Everglades marshes to the north. This mangrove transition zone is important not only as a buffer to water inputs but it is also a critical nursery area for the Bay's fish populations and a critical habitat for wading birds.

We are quantifying the nature of the mangrove transition zone with regard to the exchange of nutrients and organics with Florida Bay and the inputs of fresh water to Florida Bay. Our research emphasizes the mechanistic link between freshwater flow and materials exchanges, and the relationship between these ecologically-important processes and environmental forcing. These results will play a critical role in guiding efforts by the SFWMD and ENP to manage Florida Bay in the context of the impending restoration of historical hydrologic regimes. This research effort was initiated in August 1995, and will continue through 1998. To date, we have no results to present.

Objectives - Mangrove Wetland Transformations and Exchanges

The purpose of this portion of our overall project is to quantify the exchange of water, nutrients, and organic matter between Florida Bay and the adjacent mangrove wetlands. This will involve developing an understanding of the processes and environmental controls that influence this exchange. This information will help us predict the effect of changing freshwater inflow (e.g. changes in the timing,

http://www.aoml.noaa.gov/flbay/sali95.html (5 of 21)9/10/2007 2:32:40 PM Salinity & Nutrients-1995 spatial distribution, quantity, and quality of that inflow) on the status of the mangrove transition zone in particular and the Florida Bay estuary in general. Specific objectives are:

1. To quantify the transformations of water, nutrients, and organic materials as water passes through the wetland forests of the mangrove transition zone. This objective will entail constructing and sampling duplicate throughflow flumes in the mangrove wetlands along the Taylor River.

2. To compare patterns of water, nutrient, and organic matter exchange measured in tidal creeks of the mangrove transition zone with patterns of water residence, nutrient remineralization, and organic matter transformations mediated by the mangrove wetlands themselves. This objective will entail comparing flux data from flume studies with those from our concurrent tidal creek studies.

Methods - The Flume Technique

Throughflow flumes have been used in a number of marsh settings to quantify the exchange of nutrients and organics between an inundated wetland and the inundating water column. The basic flume technique involves removable walls placed on the marsh surface parallel to the normal flow of tidal water. Over the course of a tidal cycle, duplicate water samples are taken from both ends of the flume simultaneously and instantaneous constituent fluxes are calculated. The difference between upstream and downstream flux, or before and after treatment by the wetland within the flume, is assumed to be caused by the experimental wetland enclosed by the flume. Several researchers have used the flume technique in mangrove forests as well. We will construct duplicate side-by-side flumes in the mangrove forest near the Taylor River sampling station in May 1996, and begin sampling them in August 1996. The flumes will be sampled for several tidal cycles during quarterly sampling trips from August 1996 through August 1998.

The flexibility of the throughflow flume technique makes it possible to pursue a number of different hypotheses and approaches for the intertidal exchange portion of this study. For example, we could use the flumes to quantify sheetflow through the mangrove forest towards Florida Bay, or to quantify lateral exchanges between the mangrove forest and the Taylor River. For several reasons, we are pursuing the first question. This will involve constructing side-by-side replicate flume channels across the narrow meander neck of mangrove forest separating Florida Bay from Taylor River near the confluence. The flumes will be approximately 50m long and of variable width (between 2 and 5 m). They will be bounded by the Taylor River to the north and Florida Bay, via Little Madiera Bay, to the south. The flumes will be open at each end. Flume walls will consist of flexible plastic sheets (0.5 m high and 5 m long); they will form 2 parallel vertical walls that prevent lateral water movement as water flows through the forest. The flexibility of the plastic sheets will allow us to install the walls through the Rhizophora mangle prop roots with minimal disturbance. The walls will be supported along the flume length by attaching the plastic sheeting either to mangrove trees or to wooden stakes. The flume walls will be removed after every sampling trip, eliminating long-term impacts on the mangrove forest, preventing the accumulation of litter, and reducing edge effects.

http://www.aoml.noaa.gov/flbay/sali95.html (6 of 21)9/10/2007 2:32:40 PM Salinity & Nutrients-1995 During sampling events, when the forest within the flumes is inundated, we will draw duplicate water samples from both ends of the flumes simulaneously every 45 minutes to 1 hour, as long as the flumes are inundated. Our design will allow us to draw samples from both ends of the flumes by boat. We will analyze each duplicate sample for chlorophyll, total suspended sediments, inorganic nutrients (NH4+, NO2-, NO3- and SRP), DOC, TN, TP, TOC, alkaline phosphatase activity, salinity/conductivity, oxygen content, and temperature (all procedures will follow QA/QC-approved SERP protocols). Whenever samples are taken, we will record the water level at both ends of the flumes and note the velocity and direction of sheetflow currents through the flumes. Water flux will be calculated as the combination of advective flux (from current readings) and water volume change (from water levels). To determine water volume per unit water level, we will survey the microtopography of the mangrove wetland enclosed by each flume. Statistical analysis of flux data will be as per past marsh, mangrove, and intertidal seagrass bank flume studies. Additionally, the replicate flume design will give us more statistical power to discern whether the fluxes we measure are signficantly different from zero and are representative of red mangrove forests in general.

The Florida Bay Watch Volunteer Program

Fran Decker, The Nature Conservancy, Florida Bay Watch Program.

Florida Bay Watch is a volunteer program for people who are concerned about the water quality in Florida Bay and the Keys. The Florida Bay Watch program has a two-fold mission: 1) to collect valid, useful scientific data and information about the health and status of the Florida Bay ecosystem, and 2) to involve concerned citizens in formulating solutions to the problems in Florida Bay.

Water quality in Florida Bay has been deteriorating for many years, as evidenced by marked increases in the size and persistence of algal blooms and declines in seagrass and sponge populations. The deteriorating water quality is affecting commercial and sport fishing, and, in fact, fishing guides and commercial fishers were among the first to recognize and report the problems plaguing the bay.

Monroe County citizens have powerful motives to help develop solutions to the crisis in Florida Bay. Economic and environmental perspectives merge with respect to this issue. The Monroe County tourism economy, heavily dependent on diving and sport fishing as attractions, generated $787 million in sales in 1991. Commercial fishing generated an additional $90 million of economic activity the same year. These industries are already beginning to see impacts from deteriorating water quality.

Florida Bay Watch is a volunteer program designed to help meet the crisis in Florida Bay by ensuring that the knowledge and observations of local people are contributing to restoration efforts. Bay Watch volunteers are trained to collect a variety of data using standard methods, to report their observations of conditions in the bay, and to assist professional scientists. The data collected are passed along to cooperating agencies and, along with reports from other studies in the area, are reported through

http://www.aoml.noaa.gov/flbay/sali95.html (7 of 21)9/10/2007 2:32:40 PM Salinity & Nutrients-1995 monthly and quarterly reports. The information collected ranges from qualitative water analysis to observations on the extent of algal blooms and sponge die-offs.

The Nature Conservancy, a private, nonprofit conservation organization, is the managing partner, providing staff support and coordination. Funds are currently being provided by the South Florida Water Management District, U.S. Environmental Protection Agency, Everglades National Park, the Orvis Company, the Yamaha Outboards Miami Billfish Tournament, and many individual donors. The Florida Keys National Marine Sanctuary is contributing office space and other in-kind support for the program, and many other agencies and academic institutions are advising of cooperating with Bay Watch in important ways.

With help from professional researchers at other institutions -- including the University of Miami, Florida International University, Everglades National Park, Florida Marine Research Institute, and the Florida Institute of Oceanography -- Conservancy staff have designed Bay Watch sampling protocols to fill identified data gaps, satisfy quality control demands, and supplement professionally conducted research. A complete quality assurance plan has been filed with the Region IV office of the U.S. Environmental Protection Agency. Currently, volunteers are collecting data on five different projects: 1) An aerial survey is conducted to map the different colored patches of water in Florida Bay. Water samples are then taken from Florida Bay and analyzed to determine algal species and relative abundance, sediment load, turbidity, and salinity. This protocol is being coordinated with Florida Marine Research Institute. 2) Water samples are drawn from 25 fixed locations along the Keys and analyzed for nutrients (nitrogen and phosphorus), salinity, and contaminants. This protocol is being coordinated with Florida International University. 3) Volunteers are collecting physical water quality parameters, such as turbidity and salinity in addition to noting anecdotal observations. A preliminary data collection form is in use presently and development is expected to continue. Various fishermen, dive boat captains and eco- tour captains are participating in this project. 4) Mail-in postcards documenting fish deformities are being distributed to Florida Bay fishers, fishing guides, and resource management staff. Certain deformities are considered indicators of water-born toxins, and the results from this survey are being provided to the U.S. Environmental Protection Agency to augment its study of pollution in the South Florida ecosystem. 5) A SEACAT CTD profiler will be towed between fixed water quality sampling stations in the bay to map salinity and temperature isopleths.

The Florida Bay Watch Program will continue to work with researchers studying the bay. It is important that the program stays responsive and can expand and change as needed. Bay Watch can be expected to conduct long term monitoring of natural processes and restoration efforts.

The Florida Bay Watch Program is committed to reaching the public with current information about the state of Florida Bay. Bay Watch will be publishing results in the form of monthly and quarterly reports. There is a display at the Key Largo library featuring the maps resulting from the monthly flyovers. Bay Watch has plans for on-line access to data through the Internet. There are special events, such as presentations by partner scientists, scheduled to bring Bay Watch results to the public.

http://www.aoml.noaa.gov/flbay/sali95.html (8 of 21)9/10/2007 2:32:40 PM Salinity & Nutrients-1995 Bay Watch has grown from 7 volunteers at the Kick-off in March of 1994 to 134 volunteers presently involved. Community involvement is vital to establish a sense of stewardship. When people care about their environment, they become partners in taking care of the environment and produce constructive changes. The Florida Bay Watch program is an opportunity for the local citizens to become involved in finding solutions to the problems of Florida Bay.

Water Quality Monitoring in Florida Bay: Insights into the Geochemistry of the Subtropical Bays and Estuaries of Southwest Florida

J.W. Fourqurean, Southeast Environmental Research Program and Department of Biological Sciences, Florida International University; R.D. Jones, J. Boyer, Southeast Environmental Research, Florida International University .

Florida Bay, and the mangrove-lined estuaries and bays of the south-west coast of Florida, are unique systems in the US. They are underlain by carbonate bedrock and sedimentary deposits, and are dominated by communities of mangroves and seagrasses. Recent changes in the environments of the marine areas of Florida Bay and the Florida Keys have created a great deal of public awareness of the fragile nature of the south Florida environment. Water quality and closely related issues are at the heart of most of these recent changes. The public perceives that there have been drastic changes in the water quality of nearshore marine waters adjacent to urban and suburban areas, as well as in the waters of Florida Bay, which is more distant from obvious anthropogenic alteration. Directly adjacent to developed venetian canal systems, reduced water clarity, the loss of lobsters and reef fishes, and the loss of seagrasses is causing concern. Recent changes in Florida Bay, including hypersalinity, seagrass die- off, algae blooms, reduced water clarity, sponge mortality and fish kills have focussed national attention of the whole south Florida ecosystem. The changes in Florida Bay have in turn been blamed for recent declines in the pink shrimp harvest from the Tortugas Grounds, and declines in the vitality of the Florida Keys Barrier Reef, as evidenced by reduced water clarity, loss of coral cover, and recent occurrences of coral diseases. The data to document trends in water quality and the potential role of anthropogenic nutrient sources to these phenomena are sorely lacking.

In order to address these data needs, the Southeast Environmental Research Program (SERP) conducts monitoring of concentrations of biogeochemically reactive elements, as well as assays of the size and activity of the planktonic community, on a monthly basis at approximately 100 fixed stations in marine and estuarine areas of south Florida. These stations are located in southern Biscayne Bay, Florida Bay, and the estuarine waters of the southwest coast of Florida. In Florida Bay, sampling began summer 1989. Starting September 1992, we expanded our monitoring network up the west coast of Florida to the Lostmans River. The network was further expanded in September 1994 to include 25 stations in the estuarine areas between Lostmans River to Cape Romano. Funding for this network is provided by a number of federal and state agencies, including the South Florida Water Management District, National Park Service, and the Environmental Protection Agency.

http://www.aoml.noaa.gov/flbay/sali95.html (9 of 21)9/10/2007 2:32:40 PM Salinity & Nutrients-1995

"Water quality" is difficult to define, and means many things to many people. The term itself suggests its qualitative nature. Our program measures specific aspects of the nutrient status of the planktonic system, as well some assays of the size and activity of the microbial community. Specifically, we measure salinity, temperature, dissolved oxygen, inorganic nutrients (ammonium, nitrite, nitrate and phosphate), total nutrients (nitrogen and phosphorus), organic nutrients (carbon, nitrogen and phosphorus), turbidity, chlorophyll-a concentration and alkaline phosphatase activity. These systems typically have low concentrations of SRP (usually < 0.05 µM), high DIN (often > 100 µM), and high DOC (often > 1000 µM). The chief form of DIN in these systems is ammonium. Light attenuation, especially in the mangrove-dominated embayments, is chiefly caused by DOM. Major perturbations have occurred over the period of record, including Hurricane Andrew, poorly understood dieoff of seagrasses, and increased turbidity. Despite these perturbations, phytoplankton biomass is generally quite low (usually < 3 mg/L).

The data generated in this sampling program are proving useful to resource managers, and are providing baseline data to monitor for trends in water quality. In addition to these management-oriented uses, we are using data generated from the network to investigate specific scientific questions. Some topics presently under investigation by researchers at SERP are: regional biogeochemistry in nearshore marine systems; microbial processing of C, N and P in south Florida estuarine and marine ecosystems; budgets of biogeochemically reactive elements for the region; and the linkages between water column processes and seagrass-dominated benthic communities. A sufficiently long record of monitoring data has been collected from Florida Bay and the lower west coast so that analyses of these data are providing us with insight into budgets and processes of biogeochemically active elements. It is to be expected that the data from the recent expansions of the network will be as illuminating of processes as the Florida Bay data.

Data from the Florida Bay portion of the network has provided the basis for a more thorough understanding of the functioning of the Florida Bay ecosystem (Fourqurean et al. 1993). The phytoplankton community of Florida Bay is limited by the availability of phosphorus. On a geologic time scale, the source for phosphorus for Florida Bay has been tidal exchange with the Gulf of Mexico, with the Cape Sable region playing a particularly large role. Nitrogen is abundant in the water of Florida Bay, with ammonium as the dominant species of dissolved inorganic nitrogen. The ratios of total nitrogen to total phosphorus in the system are generally greater than 40:1. Dissolved organic carbon is present in high concentrations throughout Florida Bay.

Principle component analyses have been employed to illuminate the underlying relationships between the measured parameters in the data. The variation of each of the components in the data have been interpreted as indicative of the action of a particular process on the planktonic community. The size and activity of the heterotrophic microbial community is represented by a component variable that describes 21.2% of the original variation in the data set. The spatial variation in this component suggests that the heterotrophic community is most active in the water column of central Florida Bay. Seasonality in the original data set can be represented by a component variable that describes 20.1% of the original data. The primary contributors to the seasonality signal are temperature and dissolved oxygen. A further 13.9% of the variance in the original data was due to the variation in oxidized forms of inorganic nitrogen. Salinity variation accounted for 10.8% of the original variation and ammonium contributed

http://www.aoml.noaa.gov/flbay/sali95.html (10 of 21)9/10/2007 2:32:40 PM Salinity & Nutrients-1995 another 7.8 percent of the variation. Variation in the size of the phytoplankton community contributed another 6%. These 6 component variables could explain in total 80% of the original variation.

Declining water quality has been the cause of the loss of seagrasses from coastal areas throughout the world. It has been suggested that nutrient inputs from agriculture in south Dade county may have been responsible for seagrass die-off in Florida Bay. Our data suggest that there is no measurable nutrient impact of agriculture in south Dade county on water quality of Florida Bay. This does not preclude the potential importance of other impacts from agriculture, such as pesticide runoff or freshwater diversion, however. The most severe changes in water quality in Florida Bay that have occurred since we began monitoring have been related to turbidity events, often called algae blooms. These turbidity events began well after seagrass die-off was first noted (in 1987, Robblee et al. 1991).

The data from the SERP near-shore marine and estuarine monitoring network is providing consistent, long term data that is useful to resource managers as well as research scientists. Continuation of this monitoring effort will allow us to detect future trends in water quality, and to answer basic scientific questions about biogeochemical cycling of elements in coastal subtropical systems.

Literature Cited

Fourqurean, J.W., R.D. Jones and J.C. Zieman. 1993. Processes influencing water column nutrient characteristics and phosphorus limitation of phytoplankton biomass in Florida Bay, FL, USA: Inferences from spatial distributions. Estuarine, Coastal and Shelf Science. 36:295-314.

Robblee, M.B., T.R. Barber, P.R. Carlson, M.J. Durako, J.W. Fourqurean, L.K. Muehlstein, D. Porter, L. A. Yarbro, R.T. Zieman and J.C. Zieman. 1991. Mass mortality of the tropical seagrass Thalassia testudinum in Florida Bay (USA). Marine Ecology - Progress Series 71:297-299.

Nutrient Dynamics and Limitation in Florida Bay

Wayne S. Gardner, NOAA/GLERL, 2205 Commonwealth Blvd., Ann Arbor, MI 48105; Harvey A. Bootsma, Thomas H. Johengen, Peter J. Lavrentyev, Cooperative Institute for Limnology and Ecosystem Research (CILER), University of Michigan, Ann Arbor, Michigan 48104; James B. Cotner, Rosie Sada, Texas A&M University, Department of Wildlife and Fisheries, College Station, TX 77845; Joann F. Cavaletto, NOAA/GLERL, 2205 Commonwealth Blvd., Ann Arbor, MI 48105; Brian J. Lapointe, Harbor Branch Oceanographic Institution, Inc., Big Pine Key, FL 33043.

The definition of water quality [i.e. food web structure/activity] and nutrient cycling dynamics was specified as a major research need in the Science Plan for Florida Bay. To address this goal, investigations were conducted in August 1994 and February-March 1995 to examine (1) nutrient- limitation of phytoplankton and bacteria, (2) sediment-water nutrient fluxes and oxygen demand, (3)

http://www.aoml.noaa.gov/flbay/sali95.html (11 of 21)9/10/2007 2:32:40 PM Salinity & Nutrients-1995 water-column nutrient transformations, and (4) lower food web abundance and composition (1995 only), in selected regions of Florida Bay. Detailed bottle and sediment-chamber experiments were conducted over an east-west transect of northern-bay stations (near Duck, Rankin, and Murray Keys), and at a more central station (near Rabbit Key). Seston nutrient composition, dissolved nutrient levels, and lower food web organisms were examined at a total of 12 stations.

Nutrient limitation of phytoplankton in Florida Bay: The severity and spatial distribution of phytoplankton nutrient-limitation were assessed by measuring suspended and dissolved nutrient concentrations and ratios and by conducting nutrient enrichment experiments. Seston stoichiometry suggested that phosphorus limitation was generally more prevalent than nitrogen limitation. However, particulate C:P and N:P ratios decreased in a westerly direction within the bay, and seston stoichiometry suggested co-limitation by N and P in the western portion. Dissolved nutrient concentrations and ratios led to similar conclusions. Phosphate concentrations were very low (0.02-0.07 µM) throughout the bay, but were relatively high in the northwest. Dissolved inorganic nitrogen (ammonium plus nitrates) concentrations ranged from 0.5 µM in the southwest to 28 µM at one northeastern station. Both dissolved inorganic N:P ratios and total dissolved N:P ratios were highest in the northeast and lowest in the southwest. Nutrient enrichment assays also showed similar trends, but indicated that some stimulation of growth by nitrogen may be possible even in northeastern parts of the bay. Water samples from the northern region showed surprisingly small increases in particulate organic carbon (POC) following nutrient enrichment. In the western region, both ammonium and phosphate enhanced phytoplankton growth as measured by an increase in POC. Models predicting phytoplankton response to nutrient loading should therefore account for both N and P availability. Occasionally, enrichment with both N and P resulted in less growth than did enrichment with either nutrient separately. We conclude that other factors (e.g. microbial activities, physical and chemical conditions) can influence the relationship between nutrient availability and phytoplankton production in Florida Bay.

Experiments to determine nutritional factors limiting bacteria were conducted at our 4 main stations. Bay water was filtered (0.8 µm pore size) to remove phytoplankton and bacterial grazers and diluted 1:5 with 0.2 µm pore size filtered bay water. Respective nutrients were added to different bottles and the bottles were incubated in the dark at ambient temperature for about 15 h. Addition of amino acids and P had the greatest effect followed by additions of P alone. The strongest effect was observed at Duck Key and Rabbit Key. These data support the hypothesis that bacterioplankton undergo a transition from P- and/or C-limitation in the northeastern portion of the bay to control by other factors at more western locations.

Nutrient fluxes and oxygen demand at the sediment-water interface. Sediment-water nutrient fluxes were measured both with dark, intact sediment cores (77 mm diameter) and with in situ sediment chambers at our 4 main sites. In the core experiments, bay water was slowly (0.1 mL min-1 ) passed over the cores and differences in nutrient concentrations between inlet and outlet waters were measured. Ammonium was released from the sediments at rates ranging from approximately 2 to 40 moles m-2 h- 1. Moderate decreases (< 30%) in added 15NH4+ as the water passed over the cores suggested that partial nitrification of ammonium occurred near the sediment-water interface. Concentrations of phosphate in the water were very low (< 0.1 µM) at the different sites and did not change predictably

http://www.aoml.noaa.gov/flbay/sali95.html (12 of 21)9/10/2007 2:32:40 PM Salinity & Nutrients-1995 with passage of the water over the cores. Nitrate (including nitrite) appeared to be dynamic but its concentrations also did not change predictably. Some changes in nutrient concentrations, usually ammonium, were observed during short-term (2-6 h) in situ chamber incubations but the direction of flux was not always predictable. When changes occurred, nutrient concentrations increased more in opaque chambers than in transparent ones, an indication of immediate uptake of released nutrients by photosynthetic organisms. The Rankin and Murray stations had higher ammonium levels and occasionally higher release rates from the sediments than did the Duck and Rabbit stations. A high sediment oxygen demand (SOD = 50-250 mg O2 m-2 h-1 ) was observed at all stations. As expected, net oxygen consumption rates were generally higher in dark chambers than in light ones, especially at Rankin and Murray stations where seagrasses were not well developed or appeared "unhealthy".

Water-column nutrient transformations. Light and dark bottle experiments, with added 15NH4+ or 15N-labeled amino acids, measured autotrophic and heterotrophic nitrogen cycling rates and the response of these rates to additions of phosphorus and site-specific macroalgae. Except for the Rankin station in summer where ammonium removal was complete in a few hours, water column N regeneration rates, in bottles fortified with only 15NH4+, ranged from 0.02 to 0.12 µM h-1. Differences in N recycling rates between light and dark bottles in August were minimal at the Duck, Rabbit, and Murray stations, but were dramatic at the Rankin station in August where a bloom of the cyanobacterium, Synechoccocus was present. Ammonium-15N isotope dilution rates, as well as uptake rates were greatly increased in the light at the Rankin station, indicating a close coupling between autotrophic and heterotrophic processes. The addition of P dramatically increased the uptake and remineralization of labeled amino acids but had a minimal effect on ammonium turnover at Duck Key, an indication of heterotrophic organic-carbon limitation. The presence of macroalgae not only increased ammonium uptake but also enhanced the cycling rates of amino acid-N at Rabbit and Duck Key stations, again suggesting that bacteria were carbon-limited. This conclusion is based on the assumption that these plants release dissolved organic material that in turn fuel bacteria.

Size fractionation experiments supported the hypothesis that bacterial demand accounts for a substantial portion of the P that is recycled and is a major pathway in the P cycle in Florida Bay. Comparison of 33P uptake rates in the 0.8 µm-size class in August accounted for 50-74% of total P uptake at Duck Key, Murray Key, and Rabbit Key but only about 1% of the total uptake at Rankin Key. However, alkaline phosphatase activity was greatest at Rankin Key.

Abundances and compositions of lower food web organisms: Concentrations of chlorophyll and phytoplankton were highest at the Rankin station, where 70% of the autotrophic biovolume were due to the picoplanktonic cyanobacterium, Synechococcus sp. Changes in chlorophyll concentrations between sites were not strictly proportional to the changes observed in phytobiovolume, because of differences in the phytoplankton composition. For instance, dinoflagellates that comprised about 30% of phytoplankton at Duck Key may have had low chlorophyll content or even been heterotrophic. Note that the Rabbit and Murray stations, where POC production was greatly enhanced after nutrient enrichments, were dominated by diatoms. Abundance of both picoplankton and planktonic protists (as well as C:N:P ratio) were highest at Rankin Key. Concentrations of heterotrophic nanoflagellates (HNANO) were positively related with concentrations of picoplankton, suggesting trophic couplings between these

http://www.aoml.noaa.gov/flbay/sali95.html (13 of 21)9/10/2007 2:32:40 PM Salinity & Nutrients-1995 organisms. It is possible, that a weak response to nutrient enrichments at the Rankin station was due to top-down effects. Ciliates, that can use both bacteria and algae as food sources, also were most abundant at Rankin Key and least abundant at Rabbit Key, where phytoplankton were dominated by large (> µ30 mm) diatoms. At Duck Key, up to 30% of the ciliate population consisted of chlorophyll-bearing species. The most abundant and diverse assemblage of benthic protists was found at Rabbit Key. In contrast, protist populations were less abundant in sediments of Murray and Rankin Keys where seagrass development and dissolved oxygen concentrations were low.

Table 1. Abundance and composition of the lower food web organisms at four sites in Florida Bay (February 22, 1995).

======

Variable / Site Duck Rankin Rabbit Murray

------

Plankton Chlorophyll (µg L-1) 0.2 2.9 0.8 1.6

Phytobiovolume (µm3 105 mL-1) 4.7 29.9 7.8 12.6

Cyanobacteria (%) 5 70 2 2

Diatoms (%) 61 22 92 89

Dinoflagellates (%) 33 7 1 3

HNANO (cells 102 mL-1) 3.8 23.2 1.9 2.5

Ciliates (cells mL-1) 9.9 12.2 0.5 8.7

Protist biovolume (µm3 105 mL-1) 1.2 2.6 0.1 0.6

Bacteria (cells 106 mL-1) 6.4 11.2 4.2 5.4

......

Benthos Ciliates (cells 105 m-2) 4.7 3.8 18.8 3.6

Flagellates (cells 105 m-2) 75.3 28.1 236.1 36.0

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Conclusions: The degree of phytoplankton P-limitation in Florida Bay decreases from east to west where N becomes a co-limiting nutrient. Internal nutrient cycling in the water, as well as at the sediment- water interface, is a very important supply mechanism for available nutrients. Bacterial uptake accounts for a large fraction of water column phosphorus demand. The microbial food web plays a fundamental role in both nutrient cycling and lower food web dynamics and is an important indicator of water quality degradation and food web changes in the bay.

Nutrient Exchange Between Florida Bay and the Everglades' Salinity Transition Zone

Enrique Reyes, Coastal Ecology Institute, Louisiana State University, Baton Rouge, LA 70803; John W. Day, Jr., Brian C. Perez, Coastal Ecology Institute, Louisiana State University; Dan L. Childers, Southeast Environmental Research Program & Department of Biological Sciences, Florida International University.

The purpose of this project is to quantify the exchange of water and nutrient between Florida Bay and the adjacent mangrove wetlands and understand the processes that influence this exchange. This information will help us to understand and predict the effect of changing freshwater inflow to Florida Bay on the status of the mangrove wetland and the availability of nutrients in Florida Bay. This project started in August 1995 and will continue for the next 3 years.

We need to understand the response of the salinity transition zone that lies between the Everglades and Florida Bay to changing hydrology in south Florida. This transitional system is important because it may strongly affect the nutrient cycles of Florida Bay. The transition zone is also important because it is an essential nursery for many of the Bay's fish populations and habitat for wading birds, such as the roseate spoonbill.

The transition zone system, which is dominated by mangroves, is connected both to land and sea. Landward connection is provided by the flow of water from the Kissimmee-Okeechobee-Everglades watershed. It is likely that the ecology of the transition zone is highly sensitive to the quantity and quality of water in the watershed and thus sensitive to water management practices. Seaward connection is provided by the inflow of saline water from Florida Bay, which varies with winds and tides, as well as the opposing flow of fresh water.

With the mandate of the Everglades Forever Act, more fresh water will flow to Florida Bay through the mangrove fringe of the Bay. Furthermore, the distribution of this water will change in coming years, with an increase in flow through the Taylor Slough relative to flow through the C-111 basin. Thus, we know that water quantity and distribution is changing. However, we do not know the consequences of

http://www.aoml.noaa.gov/flbay/sali95.html (15 of 21)9/10/2007 2:32:40 PM Salinity & Nutrients-1995 these changes on the quality of water flowing into the bay. Furthermore, we do not understand the indirect effects of changing fresh water flow and salinity on nutrient cycling within Florida Bay. Understanding the link between biological and chemical dynamics in Florida Bay and hydropatterns is a necessary precursor to effectively restoring Florida Bay ecological system.

Given the apparent nutrient enrichment of Florida Bay, as evidenced by sustained algal blooms, we need to know the extent to which there is a net transport of nutrients between the Bay and these transition zone ecosystems and how this transport will be affected by water management practices as well as natural forcing functions, such as winter and tropical storms. Mangroves can affect the nutrient cycles of the Bay because they can act as a biological filter, removing nutrients from either fresh water flowing from land or seawater that pulses through the system with changing winds and tides. The efficiency of this filter may differ for different nutrients. Thus, for example, mangroves may remove and retain P, but N may flow from the Everglades into the Bay. Alternatively, with their large store of nutrients (particularly organic P within vegetation and peat) the potential exists for system to be a source of nutrients to Florida Bay. It is likely that nutrients are rapidly flushed from these systems into the Bay during storm events.

Specific objectives of this study are:

1. Define seasonal patterns of forcing functions (including frontal and tropical wave frequency, precipitation, temperature, and evapotranspiration, water levels in freshwater areas of the Everglades) affecting water and materials exchange between central and eastern Florida Bay.

2. Quantify the exchange of water and nutrients between northeastern Florida Bay and fringing mangroves in one major mangrove creek over a period of three years.

3. Compare patterns of water and nutrient exchange in major mangrove creeks along an east to west gradient.

4. Compare patterns of water and nutrient exchange, as measured in mangrove creeks, to these patterns within the adjacent mangrove wetland.

5. Synthesize information of rates of nutrient and water exchange and the factors that influence these rates in the Everglades, the mangrove wetland, and Florida Bay.

Initially, we plan to review and characterize seasonal patterns of important forcing functions which affect water and material exchange between Florida Bay and fringing mangroves. The periods of the year when flux measurements will be carried out will be chosen based on factors such as rainfall, evapotranspiration, mean sea level, water level in the upper Everglades, frequency of frontal activity and tropical wave activity, and temperature. Since the tide range is so low in Florida Bay and climatic factors play such an important role in water exchange between Florida Bay and the fringing mangroves, the sampling design for flux studies must be based on these climatic factors.

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Measurements of water and materials exchange at three tidal creeks will be carried out. During each flux study, water flow rate and instantaneous water flux, and concentrations of materials defined in the detailed work plan will be measured every 3 hours. The results of the flux calculations will be analyzed and compared to climatic forcings and management activities to determine the factors responsible for the observed fluxes.

A flume design will be used to conduct measurements of water and materials exchange between the primary tidal creek and adjacent mangroves. During each flume study, instantaneous water flux and concentrations of materials will be measured about every 2 hours when the marsh is covered with water. The results of the flux calculations will be compared to flux measurements in the primary tidal creek and other measurements (such as sediment water fluxes) in order to determine the relative importance of different processes in affecting flux of materials and water.

To integrate all the generated information, concurrently we plan to develop a predictive model of flux of materials between mangroves and Florida bay. We plan to use the model to analyze nutrient behavior under several water management regimes.

An Overview of SFWMD Research in the Florida Bay - Everglades Ecotone

D.T. Rudnick, F.H. Sklar, S.P. Kelly, Everglades Systems Research Division, South Florida Water Management District, West Palm Beach, FL.

The main objective of the South Florida Water Management District (District) research program in Florida Bay is to understand and predict the effects of changing freshwater flow on the ecology of the Bay. The focus of our ecological research is on the ecotone between Florida Bay and the Everglades. This mangrove dominated zone receives the inflow of water both from the Everglades and from marine waters and is an area with a highly variable salinity regime. It therefore is an area that is directly affected by changes in the quantity and quality of freshwater inflow and is highly sensitive to water management practices.

This research program began in the summer of 1995 and is a collaboration among researchers from the District and other institutions, including the U. of Florida (C. Montague), Florida Marine Research Institute (M. Durako), Louisiana State U. (J. Day and E. Reyes), Florida International U. (D. Childers), USGS (E. Patino), and Everglades National Park (R. Fennema). The main components of this program include studies of the relationship between freshwater flow and the flux of nutrients across the Bay - wetland interface, internal fluxes of nutrients within the northern Bay and within the mangrove wetland, and the relationship between freshwater flow and submersed macrophyte structure and productivity in the region. This research program will continue for at least 3 years.

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Field research in this program will focus on three areas along the north coast of Florida Bay: the Joe Bay- Trout Cove area, the Taylor River-Little Madeira Bay area, and the Seven Palm Lake-Terrapin Bay area. Each of these areas are important sites of freshwater inflow to Florida Bay. Salinity levels within each area potentially span a wide range along a north-south axis and each area encounters wide temporal fluctuations in water flow and salinity. These areas were also chosen because they probably span a wide range of nutrient availability, with increasing nutrients availability from east to west.

Within each area, the continous flux of nutrients over a ten-day period, through major connecting creeks (Trout Creek, Taylor River, and McCormick Creek) will be measured quarterly in association with seasonal changes in forcing functions such as freshwater flow (see abstract by Day, Reyes, and Childers). Flumes within the mangroves adjacent to a creek will measure the exchange of nutrients between the wetland and adjacent waters. Benthic nutrient flux measurements in the Bay and in ponds near these creek sites will be made simultaneously with creek flux measurements. Over a longer time- scale, net sediment accretion or subsidence will be measured at the wetland sites. This combined effort will help to determine under what conditions the mangrove ecotone is a source or a sink of nutrients and the extent to which the nutrient cycles of Florida Bay are affected by external nutrient sources.

Concurrent with these field studies of nutrient dynamics at the margin of the Bay, we will conduct studies of the temporal variability of submersed macrophytes in association with salinity and nutrient variations (see abstract by C. Montague). Salinity fluctuations have been hypothesized to be a major factor influencing the structural dynamics of the Bay's seagrass and macroalgae assemblage. This hypothesis will be tested in laboratory and field experiments.

These studies will be integrated in models of submersed macrophyte populations and the ecotone system. These component models will later be incorporated into the Everglades Landscape Model and thus help us to understand the mechanisms that link Florida Bay to the Everglades ecosystem.

Marine Physical Monitoring in Everglades National Park

DeWitt Smith, Everglades National Park.

A clear definition of long term variation in key physical variables is essential if we are to understand the estuaries of Everglades National Park. The objective of the Marine Physical Monitoring Project is to define physical conditions in the marine and estuarine parts of Everglades National Park and develop an understanding of the processes that determine these conditions. The approach we have chosen to reach this objective is to establish a series of continuous monitoring stations at key locations throughout marine and estuarine areas of Everglades National Park. We expect these stations to provide a representative long-term record of key physical parameters that will be used by project staff and other researchers addressing a variety of important research and resource management questions. Important physical parameters measured include: salinity, conductivity, temperature, water level, rainfall, wind,

http://www.aoml.noaa.gov/flbay/sali95.html (18 of 21)9/10/2007 2:32:40 PM Salinity & Nutrients-1995 and radiation. Data from the project will be used to develop a suite of marine circulation, statistical, and process based landscape models to integrate our knowledge of the system and assist our staff in evaluating management alternatives.

The South Florida Natural Resources Center at Everglades National Park has been operating a network of marine monitoring stations in Florida Bay since 1988. The accompanying map shows the location of both active and proposed sites. Instruments at these sites record water depth every 10 minutes, and at some sites, rainfall, conductivity and temperature every hour. This network is part of a larger system of physical monitoring stations located in both freshwater and marine habitats within Everglades National Park. This project was initiated in October 1987 when nine stage and rainfall monitoring stations, previously operated by the Hydrology Program, were transferred to the Marine Program. Between 1987 and 1988 nine additional stations were added to the Marine Monitoring Network in Florida Bay. All stations were upgraded from chart recorders to digital data loggers between March 1988 and January 1990. During 1991 eleven new continuous monitoring stations were added to the network, a 62% increase in network stations. Four of these stations were placed in Barnes Sound and three in northeast Florida Bay under a cooperative agreement with the South Florida Water Management District (SFWMD). An existing meteorological tower at the Joe Bay station was instrumented as part of the same agreement. The Garfield Bight water quality station was installed to monitor conditions believed responsible for fish kills in the Flamingo area. Three light stations were operated for the seagrass die-off study during 1991 and 1992. These three sites are currently being brought back on line under a cooperative agreement with the Florida Department of Environmental Protection. During this past year four stations in Florida Bay have been equipped with radio telemetry equipment allowing the park staff to check current conditions at any time. Over the next several months twelve new stations will be installed in Gulf Coast estuaries as part of cooperative projects with the SFWMD and National Biological Service Global Climate Change Project.

A Study of the Organic Carbon Flux in Florida Bay

Peter K. Swart, MGG/RSMAS, University of Miami, 4600 Rickenbacker Causeway, Miami FL 33149; Michael Lutz , MGG/RSMAS, University of Miami, 4600 Rickenbacker Causeway, Miami FL 33149.

Although there has been significant concern and research into the deterioration of water quality in Florida Bay, perhaps the most significant aspect of the factors causative in the decline of water quality has been not been addressed in any significant study. This factor is the extent of the degradation of organic material within Florida Bay. Organic material is important because through its decay it can release nutrients and consume oxygen and sulfate thereby creating anoxia and hydrogen sulfide toxicity. While significant attention has been directed at a restoration of historical salinity levels to Florida Bay, it is possible that salinity is not the problem and that fish and sponge die offs are in fact a result of oxidation of excessive amounts of organic material producing anoxia. There is no information other than that presented in this study regarding the flux of organic material through Florida Bay, the origin of the organic material, its rate of oxidation, and the effect that this oxidation has on the oxygen utilization,

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H2S, and nutrient levels.

Using data from our own studies as well as literature information, we present three methods with which to calculate a mass balance of organic carbon (OC) and distinguish between the various inputs into Florida Bay. These are (i) the mass balance approach, (ii) estimatation of the organic content of the sediments combined with the age of the bay, and (iii) the geochemical tracer approach.

The mass balance approach relies on combining the estimates of in situ production. Our present estimate is that there is approximately 1011 gms of organic carbon produced per year in Florida Bay. Based an an estimated input of between 50 and 600 km3/yr of freshwater from the Everglades and a particulate organic material (POM) content of 1200 µM/l, we can expect an additional 109 to 1010 gm/yr from this source. A further 10 to 20% organic carbon might be derived from the organic production on the mud- islands and the coastal mangrove fringe, suggesting the Everglades may account for upto 30% of the annual production of OC in Florida Bay. Production in the water column may provide upto 1010 gm/yr. 1.

An alternative approach to examining this question of OC recycling is to calculate the present amount of OC in the bay and compare it to the flux calculated in the first approach. Using these two estimates, an idea of the residence time of organic carbon and the precentage of production actually preserved in the sediments can be ascertained. As a first approximation the OC sinks in Florida Bay can be divided into two reservoirs. First, the mudbanks which comprise the vast majority of sediment contains approximately 3 x 1013 gms organic carbon. This carbon has accumulated over the history of Florida Bay and is relatively immobile. In contrast the basins contain approximately an order of magnitude less OC. This carbon is rapidly recycled and not preserved in the basins themselves, being exported into the marine environment or accumulating to form new or additions to existing mudbanks. Based on the present estimates of carbon in the bay and the estimates of production, it would appear that the carbon has a residence time of approximately 200 years. Our calculations suggest that of all the organic carbon which has been produced over the 4000 year history, approximately 3% has been retained in the sediments. This estimate is significantly higher than normal marine sediments and underlines the importance of better quantifying some of the fluxes involved.

A third approach is to use a combination of the carbon and nitrogen isotopic compositions of organic material together with parameters such as the C/N ratio to constrain the nature and the amounts of organic material contributed by end members to the system. Provided that the C/N ratios and the isotopic compositions of the various inputs are distinctive and the number of geochemical tracers are one greater than the number of significant inputs, then this approach can be used to constrain the contribution of organic material from the various sources. In a preliminary approach we have assumed that there are only two sources of organic material in Florida Bay, terrestrial and marine. The percentage of organic carbon derived from the Everglades can therefore be calculated using the bulk carbon isotopic composition of the sediment as shown in figure 2, and end members for terrestrial carbon of -25‰ and marine carbon of -8‰. Using this approach we estimate that the percentage of OC derived from the Everglades varies from as much as 70% close to Cape Sable to 30% in the center of the Bay. These estimates are higher than we predicted based on the mass flux considerations and underline the need for

http://www.aoml.noaa.gov/flbay/sali95.html (20 of 21)9/10/2007 2:32:40 PM Salinity & Nutrients-1995 further research in order to explain this apparent discrepancy.

Work which is presently being carried out involves a better calibration of the various end-members and assumptions made using the previously described approaches. In particular we are (1) carrying out a temporal and spatial investigation of the amount and isotopic composition of POM in the water column, (2) examining methods with which we might characterize the rate of decomposition of organic material, (3) refining a model which will account for the cycling of OC from the Everglades into Florida Bay. This work is essential if we are to understand the links between nutrients, the development of anoxia and the die-off of sea grasses and other organisms in the bay.

Last updated: 07/16/98 by: Monika Gurnée [email protected]

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Seagrass Ecology

1995 Abstracts

Florida Department of Environmental Protection's Fisheries Habitat Assessment Program (FHAP):An Assessment of Macrophyte Distribution and Abundance on a Florida Bay-Wide Scale

M. J.Durako, M.O. Hall, P.R. Carlson, Florida Department of Environmental Protection, Florida Marine Research Institute, 100 Eighth Ave. S.E., St. Petersburg, FL 33701.

Since 1988, research at the Florida Department of Environmental Protection's Florida Marine Research Institute (FMRI) has focused on ecosystem responses and possible causative factors related to the widespread decline and loss of seagrasses in Florida Bay. Early studies examined structural and dynamic changes in the seagrass community associated with seagrass die-off (Durako, 1995). Other studies have, 1) elucidated the roles of hypoxic stress and sulfide toxicity in die-off (Barber and Carlson, 1993; Carlson et al., 1994), 2) examined the physiological effects of infection by the marine slime mold Labyrinthula sp. on the dominant seagrass, Thalassia testudinum (Durako and Kuss, 1994), and 3) have compared changes in Thalassia short-shoot demographics related to die-off (Durako, 1994). In 1994, 33 winter and 108 summer stations, previously sampled in 1983/84 (Zieman et al., 1989), were resampled to compare quantitative changes that have occurred over the last decade in the distribution and abundance of the dominant macrophytes (seagrasses and macroalgae). Preliminary analyses of these data indicate that that the overall distribution patterns of the three dominant seagrasses have exhibited little change, but that abundance and biomass of the three dominant seagrasses has declined dramatically in the central and western regions of the Bay. The areas of greatest decline corresponded to those basins that have experienced the most severe die-off and areas subjected to chronic turbidity due to microalgal blooms and resuspended sediments. Demographic analyses of Thalassia testudinum short-shoots collected from several western basins over a period extending from 1989 to 1994 indicate that this species is in a continuing state of decline, but that the mechanism for the decline has changed. To expand the geographic scope and resolution of information on the distribution and abundance of the dominant macrophytes and the demographics of Thalassia in Florida Bay, FMRI initiated the Fisheries Habitat Assessment Program (FHAP) in 1995. In FHAP, 30-35 stations in each of ten basins will be sampled twice yearly using an EMAP-compatible hexagonal grid system. A combination of Braun- Blanquet frequency/abundance sampling and quantitative, core sampling will be conducted during the spring (low stress period); Braun-Blanquet sampling will also be conducted during the fall (high stress period) in order to examine intra- and inter-annual changes in macrophyte distribution and abundance. Ten short-shoots are collected at each station for determination of occurrence of potential microbial pathogens (especially Labyrinthula). Spatial analyses of cover/abundance data from 332 stations sampled in April of 1995 indicate that Thalassia abundances were lowest (<5-25% cover) along the

http://www.aoml.noaa.gov/flbay/seag95.html (1 of 17)9/10/2007 2:32:42 PM Seagrass Ecology-1995 northern boundary of Florida Bay and that they increased from the northeast to southwest. Halodule exceeded 5% cover only in basins in north central Florida Bay. Syringodium was present only in the southwestern Bay. Drift-red macroalgae and Batophora exhibited highest abundances along the northeastern Bay margin. With present funding, FHAP will continue at least through the summer of 1996.

References:

Barber, T. R., Carlson, P. R. Jr. 1993. Effects of seagrass die-off on benthic fluxes and porewater concentrations of SCO2, SH2S, and CH4 in Florida Bay sediments. In: R. S. Oremland (ed.), Biogeochemistry of Global Change: Radiatively Active Trace Gases, Chapman and Hall, New York, pp. 530-550.

Carlson, P. R. Jr., Yarbro, L. A., Barber, T. R. 1994. Relationship of sediment sulfide to mortality of Thalassia testudinum in Florida Bay. Bull. Mar. Sci. 54(3):

Durako, M. J. 1994. Seagrass die-off in Florida Bay (USA): changes in shoot demography and populations dynamics. Mar. Ecol. Prog. Ser. 110:59-66.

Durako, M.J. 1995. Indicators of seagrass ecological condition: An assessment based on spatial and temporal changes associated with the mass mortality of the tropical seagrass Thalassia testudinum. Pp. 261-266 In: K.R. Dyer and C. F. D'Elia (eds.) Changes in fluxes in estuaries: implications for science to management. Olsen and Olsen, Fredensborg, Denmark.

Durako, M. J. and K. M. Kuss. 1994. Effects of Labyrinthula infection on the photosynthetic capacity of Thalassia testudinum. Bull. Mar. Sci. 54(3):727-732.

Zieman, J. C., Fourqurean, J. W., Iverson, R. L. 1989. Distribution, abundance and productivity of seagrasses and macroalgae in Florida Bay. Bull. Mar. Sci. 44(1): 292-311.

Long-Term Seagrass Monitoring Stations on Cross Bank: The Effects of Long-Term Manipulation of Nutrient Supply on Competition Between the Seagrasses Thalassia Testudinum and Halodule Wrightii in Florida Bay

James W. Fourqurean, Southeast Environmental Research Program and Department of Biological Sciences, Florida International University; George V.N. Powell, RARE, Inc.;W. Judson Kenworthy, Beaufort Laboratory, NMFS; Joseph C. Zieman, University of Virginia.

As part of an experiment investigating the long-term response of Florida Bay seagrass beds to increased

http://www.aoml.noaa.gov/flbay/seag95.html (2 of 17)9/10/2007 2:32:42 PM Seagrass Ecology-1995 nutrient availability, we have been monitoring species composition and abundance of 5 seagrass beds on Cross Bank in Florida Bay. Long term (11y) continuous fertilization (via application of bird feces) of established seagrass beds in Florida Bay caused a change in the dominant seagrass species. Prior to fertilization, the seagrass beds were a Thalassia testudinum monoculture; after 11 y of fertilization the seagrass Halodule wrightii made up 97% of the aboveground biomass. Fertilization had a positive effect on the standing crop of T. testudinum for the first two years of the experiment. The initial response of T. testudinum to increased nutrient supply was an increase in the leaf biomass per short shoot. Increased leafiness is a well-known plant response to shading, and there is some evidence that T. testudinum may respond to decreased light availability by increasing shoot size. In our experiments, however, T. testudinum shoot size decreased after 1984 , as light availability continued to decrease concomitantly with increases in H. wrightii biomass. This suggests that the initial increase in T. testudinum shoot size was a response to increased nutrient availability, not decreased light availability.

The transition from T. testudinum-dominated to H. wrightii -dominated was dependent on the timing of colonization of the sites by H. wrightii; the decrease in T. testudinum standing crop and density at the fertilized sites occurred only after the colonization of the sites by H. wrightii. There were no trends in the standing crop or density of T. testudinum at control sites, and none of the control sites were colonized by H. wrightii.

Nutrient availability has been correlated with epiphyte loads on seagrass leaves, and shading of seagrasses by epiphytes has been implicated as one of the most deleterious effects of eutrophication of seagrass habitats. Since leaf turn-over is faster for H. wrightii than T. testudinum, it is conceivable that fouling of the longer-lived T. testudinum leaves could cause the loss of T. testudinum from areas of nutrient enrichment, but this mechanism was probably not operative in these experiments. While the epiphyte loads of the seagrasses at fertilized and control sites were not quantified, there were no visual differences in macrophytic or microscopic epiphyte loads at control or fertilzed sites.

The effects of fertilization on these seagrass beds persisted at least 11 y after the cessation of nutrient addition. In 1994, the species composition of seagrass beds that had fertilization discontinued in 1983 were still markedly different than control beds. Halodule wrightii was common at these sites where nutrient addition was stopped. These results suggest that seagrass beds in Florida Bay efficiently retain and recycle acquired nutrients.

Results of these experiments suggest that Halodule wrightii, the normal early-succesional seagrass during secondary succession in Caribbean seagrass communities, has a higher nutrient demand than Thalassia testudinum, the normal late successional species, and that the replacement of H. wrightii by T. testudinum during secondary successsion is due to the ability of T. testudinum to draw nutrient availability below the requirements of H. wrightii.

In the fertilization experiments presented here, Halodule wrightii was clearly favored by fertilization. Fertilized sites eventually converged on similar, H. wrightii-dominated seagrass beds, but the trajectories of the individual sites was dependent on the colonization of the sites by H. wrightii. In the absence of H.

http://www.aoml.noaa.gov/flbay/seag95.html (3 of 17)9/10/2007 2:32:42 PM Seagrass Ecology-1995 wrightii, Thalassia testudinum biomass stayed elevated over control areas, but following the eventual colonization of the sites by H. wrightii, T. testudinum declined. The stochastic event of H. wrightii colonization therefore controlled the response of Florida Bay seagrass beds to manipulations in resource supply rates.

Interpretation of the results of this experiment was dependent on the duration of the fertilization of the seagrass beds. Increased nutrient availability caused a doubling of the Thalassia testudinum leaf biomass over controls for the first two years of this experiment; and were it to have ended at that time we would have concluded that increased nutrient supply to Florida Bay seagrasses would cause an increase in the biomass of the late successional seagrass T.testudinum. The true outcome of such a change in nutrient supply rates was dependent on the colonization of these fertilized, and therefore newly-suitable, areas by the early successional seagrass Halodule wrightii. This time-dependent result underscores the importance of designing field experiments of the proper duration to capture the dynamics of the system being studied.

Seagrass Cover-Abundance and Distribution in Northeast Florida Bay Downstream From the C-111 Canal and Taylor Slough

Lee Hefty, Metropolitan Dade County Department of Environmental Resources Management.

In October 1993, six monitoring stations were established in northeast Florida Bay to document water quality and biological characteristics (seagrass) in the near shore habitats downstream from the C-111 \Taylor Slough watershed. A series of water quality parameters and seagrass shoot and blade density data were collected monthly at each station. A cursory review of the data revealed seagrass distribution and species composition appear to be related to overall mean annual salinity. Thalassia testudinum was the dominant seagrass at four out of six stations. T. testudinum was found at four stations which exhibited highest annual mean salinity and narrowest salinity range. These stations were located in basins which were less geographically isolated and more likely to experience water exchange with neighboring basins (i.e. Long Sound, Trout Cove, and Little Madeira Bay). Halodule beaudettei (formerly H. wrightii) and Ruppia maritima were found together as dominant components of the benthic community at two stations located in Highway Creek and Joe Bay . These basins are somewhat geographically isolated and are therefore more likely to be influenced by upland runoff than by direct exchange with neighboring basins. These stations exhibited a wider annual salinity range and overall lower annual mean salinity. T. testudinum mean shoot density ranged from 205 to 376 shoots/m2. H. beaudettei mean shoot density ranged from 0 to140 shoots /m2 when growing heterogeneously with T. testudinum, and from 80 to 860 shoots/m2 when found growing heterogeneously with R. maritima. R. maritima was consistently found with H. beaudettei and exhibited mean shoot densities of 170 -1200 shoots /m2.

Introduction

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In an effort to address concerns regarding the flow of freshwater to the east Everglades and Florida Bay, regional water managers began to increase water delivery to Taylor Slough in June 1993. As a requirement of the Monitoring and Operating Plan for the C-111 Interim Construction Project, and as recommended by the Taylor Slough Demonstration Project, a water quality and biological monitoring project was undertaken to monitor the downstream effects of this change in water delivery. The South Florida Water Management District (SFWMD) contracted with the Metropolitan Dade County Department of Environmental Resources Management (DERM) to perform water quality and biological monitoring in northeast Florida Bay. In October 1993, DERM established six monitoring stations in northeast Florida Bay. Site locations were determined by SFWMD staff members and were based on proximity to existing water quality stations in basins believed to be influenced by the changes in water management practices. The six stations were oriented to form three north-south transects in the area from Little Madeira Bay eastward to US Highway 1. Each station is sampled monthly for a series of physical water quality parameters and biological characteristics.

The objectives of the study are; 1) To provide baseline data and document changes in the benthic communities of northeast Florida Bay downstream from the C-111\Taylor Slough watershed; 2) To provide baseline data on existing water quality conditions, and document changes in water quality in the surface waters associated with these benthic communities.

Project Methodology

Station Locations

Station Lat\Long Station Lat\Long

Highway Creek 25.2549 \ 80.4451 Long Sound 25.2349 \ 80.4586

Joe Bay 25.2296 \ 80.5263 Trout Cove 25.2169 \ 80.5187

Taylor River 25.1907 \ 80.6355 Little Madeira Bay 25.1741 \ 80.6328

Surface Water Quality Monitoring

In situ physical water quality measurements are collected monthly at each station. A calibrated Hydrolab Surveyor II multi-parameter analyzer is used to collect temperature, pH, dissolved oxygen, conductivity, oxidation/reduction potential, salinity, and depth at each site. A Licor LI 1000 integrating photometer with two 4 pi sensors are used to measure photosynthetically active radiation (PAR). PAR data is used to derive the extinction coefficient KdPAR for the water column at each site. All parameters (except PAR) are collected at the surface, at one meter (where depths allow) and the bottom.

Biological Monitoring (Seagrass)

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Each station consists of a 50 meter transect with three randomly located fixed one meter square sampling areas. Transect locations are marked with submerged buoys, and sampling grid locations are marked with cut rebar. A 1m x 1m portable grid is placed in each sampling area and shoots and blades are counted for each species of seagrass present within five randomly chosen 20 cm x 20 cm subunits (Only shoots are counted for Halodule beaudettei and Ruppia maritima). A modified line-intercept method is used to assess seagrass cover and the presence of other macrophytes along the transect. Standing crop biomass is collected quarterly from three 20 cm x 20 cm plots adjacent to the transect at each station. A representative aliquot of ten blades is selected for determining epiphyte loading. Epiphytes are removed by scraping and each fraction is dried in an oven at 60 degrees C and then weighed.

Conclusions

Review of the data and sampling methodology revealed limitations in the statistical integrity of data interpretation. This fact coupled with the efforts of the Interagency Work Group on Florida Bay to standardize sampling methodology have lead to modification of the sampling methods previously used for this project. Modified sampling methods have been derived using guidelines from other studies currently being conducted in Florida Bay and in the Florida Keys National Marine Sanctuary. The modified methods will be implemented in November 1995. The design is comprised of two main elements. The first is a high frequency scattered random sampling that provides status and spatial data on water quality and benthic communities on a basin-wide scale. The second is a lower frequency, repeated sampling of fixed locations in several basins.

Scattered Random Sampling

A study region will be identified within each basin. Each study region will follow basin contours excluding edge effects created by shorelines and islands. Each large study region will be divided into 12 approximately equal subregions (i.e., Long Sound, Little Blackwater Sound, Joe Bay, and Little Madeira Bay), and each small study region (i.e., Highway Creek, Blackwater Sound, Alligator Bay, Devils Cove, Trout Cove, and south of Little Madeira Bay) will be divided into four equal subregions. Each subregion will be further divided into nine sections. A section from each subregion will be randomly selected on a monthly basis and sampled. Sample locations are defined as the approximate center of each section. The sample site location [latitude and longitude] will be derived using geographic information systems (GIS) based software. Navigation to each site will be accomplished using a global positioning system (GPS).

At each sample site, four 0.25m2 quadrats will be randomly placed off the boat. Each quadrat will then be assessed using the Braun-Blanquet cover-abundance scale (BBCA). A BBCA rating will be recorded for each species of seagrass and major macroalgal groups present within the quadrat. The BBCA scale will be defined as follows ( 5 = >75%; 4 = <75,>50%; 3 = <50,>25%; 2 = <25,>5%; 1 = <5% numerous; 0.5 = <5% sparse; 0.1 = <5% solitary).When possible, seagrass shoot and blade densities will be recorded in a 0.0625m2 subsection of the quadrat.

http://www.aoml.noaa.gov/flbay/seag95.html (6 of 17)9/10/2007 2:32:42 PM Seagrass Ecology-1995 Fixed Repeated Sampling

Sample sites will be the existing six stations established in October 1993 with one additional station in Blackwater Sound.

Sampling techniques will consist of a modified version of the techniques used at these stations over the last two years. Each station will consist of a 50 meter transect with three randomly located fixed one meter square sampling areas. A 1m x 1m portable grid will be placed in each sampling area and shoots and blades counted for each species of seagrass present within five randomly chosen 20 cm x 20 cm subunits. Each quadrat will then be assessed using the Braun-Blanquet cover-abundance scale (BBCA). A BBCA rating will be recorded for each species of seagrass and major macroalgal groups present within the quadrat.

Biomass samples will be collected semiannually in the early spring and late fall. Five 8" diameter core samples will be collected adjacent to each station. The sample will be rinsed in the field to remove sediment and kept frozen in freezer bags until processed in the laboratory. In the laboratory the sample will be thawed then rinsed to remove remaining sediment and sorted into groups of seagrass by species, and macroalgae. The number of short shoots, leaf number, leaf length and width measurements will be made on intact Thalassia testudinum shoots. Each seagrass group will then be divided into fractions representing live rhizomes and roots, dead rhizomes and roots, dead shoots, live shoot stems, leaf sheaths, green blades, and brown blades. Epiphytes will be removed by scraping. All fractions will be rinsed in 10% HCl then dried in an oven at 60 degrees C and weighed. Macroalgae will be rinsed then sorted into major groups and dried in an oven at 60 degrees C and then weighed.

Surface Water Quality Monitoring

In situ physical water quality measurements will be collected monthly at each selected scattered random site, and semiannually at each fixed repeated site.

Resource Health Issues in Florida Bay: Linking Disease and Mortalities

Jan H. Landsberg, Barbara A. Blakesley, Florida Department of Environmental Protection, Florida Marine Research Institute, 100 Eighth Ave S.E., St. Petersburg, FL. 33701.

Since 1987, studies in Florida Bay have documented sea grass die offs, mangrove and sponge mortalities, fish kills, and tumors in turtles. Overall evaluation of these disease and mortality events indicates that they are signals of an ecosystem in distress. In addition to impacting the macro-biota, changes in environmental factors such as wide fluctuations in salinity, temperature, light, turbidity, sediment suspension, and nutrient distribution have contributed to increases in phytoplankton blooms, in particular those of the cyanophyte (Synechococcus elongatus). In such a highly dynamic ecosystem, the

http://www.aoml.noaa.gov/flbay/seag95.html (7 of 17)9/10/2007 2:32:42 PM Seagrass Ecology-1995 partitioning of the effects of each of the various stressors is often not possible because of an increased susceptibility of organisms to disease and mortality. The underlying key to understanding health issues in Florida Bay is the systematic evaluation of the basic role and subsequent interactions of potential stressors. A holistic, epizootiological approach is being developed that incorporates the impacts of "a dysfunctional system" on specific aquatic organisms and attempts to determine the interactions between natural and anthropogenic stress, biotoxins, contaminants, and disease.

The role of the slimemold Labyrinthula sp. in the seagrass die-off beginning in 1987 was considered to be that of a secondary pathogen that infected stressed, weakened Thalassia (Robblee al., 1991). In April 1995, we investigated the distribution of Labyrinthula sp. in Thalassia testudinum and began a study to evaluate its role in disease and associated mortality in this seagrass. Labyrinthula sp. was found in lesions that were characterized by thin, brown, longitudinal streaks along the leaf blade. In fresh squash leaf preparations Labyrinthula sp. was typically present at the leading edge of the lesion. We investigated prevalence levels of Labyrinthula sp., adapted some field techniques to rapidly screen for Labyrinthula sp., and evaluated the presence and distribution of leaf lesions. We are also refining histological techniques and staining methodologies to study the pathology of Labyrinthula sp. in Thalassia leaves and scanning electron microscopy techniques to examine the morphology and the surface leaf distribution of Labyrinthula sp. on leaf blades. Baseline microbiology screens are being performed on Thalassia and techniques for axenic culture of Labyrinthula sp. are being developed. In addition, a full health profile of Thalassia will be developed through investigation of other potential pathogens, such as viruses, bacteria, and fungi (Florida Bay Science Plan [1994], Question 1 in "Seagrass, Mangrove and Hardbottom Habitats", Task vi).

Seagrass samples were obtained from field surveys being conducted by Durako et al. (this meeting), and shipped daily to FMRI in St. Petersburg. Leaf blades were examined for % lesion cover and presence or absence of Labyrinthula sp. A total of 10,516 Thalassia leaves were examined from 306 sites in 10 Florida Bay basins. A range of 27 to 35 sites were examined from each basin. Whenever possible, at least 10 individual shoots were examined from each site. Prevalence of infected seagrass (n) ranged from 0.0% at Eagle Key (n = 33), 2.9% at Crane Key (n = 35), 3.45% at Madeira Bay (n = 29), 3.7% at Whipray (n = 27), 6.7% at Calusa Key (n = 30), 7.1% at Blackwater Sound (n = 28), 10.3% at Rankin Lake (n = 29), 23.53% at Rabbit Key (n = 34), 25.81% at Twin Keys (n = 31) and 33.3% at Johnson Key (n = 30). A significant difference (t-test, n = 304, P < 0.0001) was noted between the mean % lesion cover of infected (2.35%) and uninfected (0.245%) shoots at all sites. The number of lesioned leaves per shoot varied by site. Typically, older shoots with a higher leaf number had more lesions, and outer leaf blades were more heavily infected than new leaves. The mean total % of leaves (n) with lesions varied by site from 4.2% at Eagle Key, 3.53% at Crane Key, 6.23% at Madeira Bay, 11.2% at Whipray, 9.22% at Calusa Key, 12.9% at Blackwater Sound, 12.6% at Rankin Lake, 30.4% at Rabbit Key, 9.0% at Twin Keys and 36.3% at Johnson Key. Evaluations for Labyrinthula sp. in fresh squash preparations of lesioned leaves were conservative in that not every lesioned plant was found to be infected. Heaviest infections by Labyrinthula sp. were noted in the central portion of Florida Bay at Twin Keys, Rabbit Key, and Johnson Key. The question remains as to whether heavily infected seagrass beds are in areas that were not decimated by the earlier die off such as was described in Rankin Lake (Robblee et al. 1991) and therefore are still susceptible to disease. Initial indications suggest that Labyrinthula sp. may

http://www.aoml.noaa.gov/flbay/seag95.html (8 of 17)9/10/2007 2:32:42 PM Seagrass Ecology-1995 be more significant in seagrass die off than is currently recognized. Spatial and temporal trends in the distribution of Labyrinthula sp., % leaf lesion cover, and overall seagrass health will be determined twice yearly for 3 years (in conjunction with the study of Durako et al. this meeting). Studies on the life history and transmission of Labyrinthula sp. are in progress. Additional lesioned Thalassia was obtained from areas near the Florida Keys island chain (N. Diersing, FMRI, pers.comm.), examined, and Labyrinthula sp. was identified. Labyrinthula sp. has also been found in Halodule wrightii leaves exhibiting characteristic lesions. This Labyrinthula sp. will be identified and compared to the Labyrinthula sp. from Thalassia.

The presence of persistent blooms of the cyanophyte Synechococcus elongatus has been associated with sponge mortalities in Florida Bay. Other negative impacts of this cyanophyte upon aquatic organisms have not been well documented. We have recently obtained mussels Brachidontes exustus from heavily populated areas in Florida Bay (W. Lyons, this meeting), acclimated them to laboratory conditions at 30 ppt, and have maintained them on a subsistence diet of Cyclotella sp. and Isochrysis sp. (K. Steidinger & W. Richardson, FMRI, unpublished). Cultures of Synechococcus elongatus have been maintained in the microalgal culture collection at FMRI. We will use feeding studies to investigate the effects of different densities of Synechococcus on these mollusks. Health evaluations will determine potential effects on growth, feeding, and susceptibility to disease (Florida Bay Science Plan [1994], Question 1 in "Living Resources", Task i - health and condition of organisms). Health evaluations of B. exustus obtained from the molluscan mapping study will also be carried out.

In addition, we plan to experimentally examine the potential effects of Synechococcus on the health of resident fish species such as the rainwater killifish (Lucania parva) or the goldspotted killifish (Floridichthys carpio). Fish will be exposed to different densities of Synechococcus in the laboratory and studied for behavioral changes, susceptibility to disease, and presence of histopathology. Health evaluations will determine changes in parasite densities, and determine pathology in target organs such as gills, spleen, liver, kidney, and intestine. This study will be part of an overall field health assessment of fish, decapod, and seagrass samples that will be obtained from the faunal community study of seagrass beds at the eight different locations in the Bay described by Matheson et al. (this meeting). Seagrass samples will be studied using the same techniques as described above. The rationale will be to determine if areas with unhealthy, lesioned seagrass are a signal of a generally unhealthy habitat and whether the health of fish and decapod residents becomes similarly compromised. Our health assessment is designed to measure sensitive changes in fish and decapod health and comprises a combination of disease, parasite, and pathology studies. By studying the parasite assemblages of target organisms together with changes in fish or decapod morphometrics, organosomatic indices, and pathology of selected tissues, an overall comparative health index will be developed. Common parasite species that may be good indicators of changing environmental conditions may also be selected for study. For example, the dinoflagellate Crepidoodinium cyprinodontum is a unique photosynthetic parasite that lives on the gills of some killifish. This parasite is likely to be influenced by ambient light levels and its presence may signal optimal light regimes, or conversely its absence may signal turbid conditions (Florida Bay Science Plan [1994], Question 1 in "Living Resources", Task i - health and condition of organisms).

http://www.aoml.noaa.gov/flbay/seag95.html (9 of 17)9/10/2007 2:32:42 PM Seagrass Ecology-1995 Fish kills have been frequently reported in Florida Bay. There is a pressing urgency to establish protocols to determine the nature of these fish kills and obtain samples rapidly for diagnosis. We need to develop methods for recovery and shipment of organisms for timely examination. We wish to examine water samples for natural algal blooms that could be toxic to fish, for physico-chemical factors such as low dissolved oxygen, or for pesticides introduced into the Florida Bay ecosystem. Sediment, water, and biotic samples should also be examined to obtain baseline contaminant information. Plans are being developed in conjunction with the FDEP chemistry laboratory in Tallahassee (B. Coppenger & T. Fitzpatrick), and FDEP, FMRI laboratory in Marathon (J. Hunt) to complement existing contaminant studies (Scott et. al.; Summers et al.; this meeting) in Florida Bay. Muscle, gonad, and liver samples from selected fish species will be examined for contaminants in parallel with a fish health evaluation similar to that described above (Florida Bay Science Plan [1994], Question 1 in "Living Resources", Task i - health and condition of organisms, and Question 4 in "Water quality and nutrient cycling", task vii).

Fish kill events should be interpreted with caution and we need to ensure that a full analysis of all possible samples is completed. This is a critical process to ensure that kills are not immediately "blamed" on anthropogenic inputs or the current "dysfunctionality" of Florida Bay. These fish kills need to be evaluated in the full context of natural and anthropogenic phenomena. Contaminants can and should be examined but only together with a full suite of other diagnostic procedures. It is hoped that efforts for coordination will be discussed by the National Park Service, the Department of Environmental Protection, and other cooperating agencies to maximize data collection efforts and facilitate coordination in the interpretation of results. The occurrence of fish kills should be entered into a Florida Bay database that also includes other mortality and disease events. A holistic approach to such events will aid in the identification of "hot spots" and temporal and spatial trends that may not otherwise be apparent.

The Influence of Salinity Fluctuation on Submersed Vegetation at the Land Margin of Northern Florida Bay

Clay L. Montague , Associate Professor, Department of Environmental Engineering Sciences, University of Florida.

Field monitoring of biota and water quality at 12 stations in northeastern Florida Bay south of C-111 canal 11 times during 1986 and 1987 revealed very low densities of submersed vegetation and associated fauna. The best correlate with total station biomass was the standard deviation of the 11 salinity spot checks made at each station. This led to the hypothesis that salinity fluctuation -- possibly assisted by high temperatures and low nutrients -- prevented the sustained development of healthy communities of submersed vegetation at the land margin of northern Florida Bay (see Montague and Ley 1993, Estuaries 16(4): 703-717). If this hypothesis is true, then gaining control over salinity fluctuation in northern Florida Bay means gaining control over the biomass of submersed vegetation.

http://www.aoml.noaa.gov/flbay/seag95.html (10 of 17)9/10/2007 2:32:42 PM Seagrass Ecology-1995 Control may be within the power of society if management decisions for the C-111 canal influence salinity fluctuations in northern Florida Bay. Hence, it is important to test the salinity fluctuation hypothesis.

Six testable predictions can be made based on this hypothesis: 1) experimental exposure of submersed vegetation to salinity fluctuation should elicit a negative physiological response in the plants; 2) shifts in submersed plant biomass and community composition should follow changes in salinity; 3) submersed plant biomass should be higher both upstream and downstream of the zone of maximum salinity fluctuation; 4) plants transplanted out of areas of high salinity fluctuation should flourish, while reciprocally transplanted plants should grow poorly; 5) total plant biomass should negatively correlate to the degree of salinity fluctuation among areas of similar mean salinity; and 6) a computer simulation model of the plant response to salinity fluctuation should predict the distribution of submersed vegetation near the land margin of northern Florida Bay. Funding has just been made available to the University of Florida by the South Florida Water Management District to test these predictions, no data are yet available.

Benthic Macrophyte and Invertebrate Distribution and Seasonality in the Florida Bay - Everglades Ecotone: Influence of Salinity Variation

Douglas Morrison, Everglades System Restoration Office, National Audubon Society, Miami.

This project will investigate the influence of salinity fluctuation on the seasonal abundance and distribution of benthic macrophytes and invertebrates in the Everglades - Florida Bay ecotone. This study will provide baseline data to assess the ecological effectiveness of management actions to restore more natural freshwater inflow patterns. The study will also provide information to identify and evaluate potential biological indicators of freshwater inflow patterns. This project is designed to complement and integrate with other ongoing and proposed macrophyte studies in the ecotone and Florida Bay. Field sampling will begin in October 1995 and continue for one year.

The geographic focus of the study is the lakes and embayments along the mainland shore of north Florida Bay from Seven Palms Lake west to Lake Ingraham. Specific study sites will include Seven Palms Lake, Monroe Lake, Terrapin Bay, West Lake, Long Lake, The Lungs, Garfield Bight, Cuthbert Lake, Coot Bay, Bear Lake, and the unnamed water body between West Lake and Lake Ingraham. Two sets of study sites will be oriented along the salinity gradient from inland to the Bay. These are: Seven Palms Lake to Terrapin Bay and West Lake to Garfield Bight. These will complement existing FDEP seagrass monitoring sites seaward in Florida Bay.

Two sampling regimes will be used for submerged macrophytes. All study waterbodies will be surveyed twice-yearly, in October (end of wet season) and April-May (end of dry season) to assess species distribution and abundances on a waterbody-wide scale. Ten randomly located 50m transects will be

http://www.aoml.noaa.gov/flbay/seag95.html (11 of 17)9/10/2007 2:32:42 PM Seagrass Ecology-1995 surveyed for macrophyte percent cover in each study waterbody. These transects will be marked so that the same transect can be sampled in both periods. GPS coordinates will be recorded for all study sites and transects. Five to ten 0.25m2 quadrats at random locations off each transect will be sampled for macrophyte percent cover using a modified Braun-Blanquet cover-abundance scale (same as FDEP). This sampling regime will provide information on macrophyte composition, distribution, and abundance in wet and dry seasons on a relatively large spatial scale.

More detailed and frequent sampling to evaluate macrophyte seasonality and the influence of salinity fluctuation will be conducted in a subset of study waterbodies. At this time, these waterbodies include Seven Palms Lake, Terrapin Bay, West Lake, and Garfield Bight. One or two additional waterbodies will likely be added after further exploratory surveys. Macrophyte species composition and abundance will be surveyed every two months at one site in each of the selected waterbodies. Macrophyte biomass will be harvested from 10 randomly located 0.25m2 quadrats at each site during each sampling period.

All study waterbodies will be surveyed twice-yearly, in October (end of wet season) and April-May (end of dry season), for benthic infauna. At least 10 randomly located 15 cm diameter sediment cores will be collected in each study waterbody for each sampling event. Infauna will be separated from sediment using a 0.5mm sieve. Invertebrate species and number of individuals will be recorded.

The following physicochemical parameters will be sampled at least once each month in each study waterbody: salinity/conductivity, temperature, irradiance and extinction coefficient, dissolved oxygen, pH, and turbidity. Nutrients (total phosphorus, ammonium, nitrate/nitrite) will be sampled every month at sites with detailed (every two months) macrophyte monitoring.

Benthic Macrophyte Seasonal and Longer-Term Patterns in Florida Bay Along the Key Largo Shoreline

Douglas Morrison , Everglades System Restoration Office, National Audubon Society, Miami, FL.

In 1979 and 1980, I investigated seasonality in macrophyte communities dominated by Batophora oerstedi in Florida Bay along the upper Keys shoreline. This study assessed seasonal patterns in macrophyte assemblages and Batophora seasonality in photosynthesis, respiration, abundance, and reproduction. Seasonal differences were observed in species richness, species diversity, total vegetational abundance, and the abundances of individual species. Ten species varied seasonally in abundance, including the dominants: Batophora, Laurencia spp., and Acetabularia crenulata. Some species (e.g., Batophora) were more abundant in summer; other species (Laurencia, Acetabularia) were more abundant in winter. Macrophyte associations can be subdivided into summer and winter dominated communities. Batophora photosynthesis, respiration, and reproduction also varied seasonally. Temperature is the major abiotic causal factor of macrophyte seasonality here.

http://www.aoml.noaa.gov/flbay/seag95.html (12 of 17)9/10/2007 2:32:42 PM Seagrass Ecology-1995 In 1994 and 1995, I resurveyed two of these sites to evaluate any long-term (14 years) changes in these macrophyte communities. These sites are a natural bay flat and a finger canal near Hammer Point on Key Largo. Macrophyte species composition and abundance (percent cover) were surveyed in March 1994 (winter), September 1994 (summer), and March 1995 using a point intercept method in randomly located 0.25m2 quadrats (25 points per quadrat). At least 20 quadrats were sampled at each site during each sampling event.

I also collected biomass samples for Batophora, Laurencia spp., and Acetabularia in March, June, September, and December 1994 (10 0.2m2 quadrats each site, each period).

Macrophyte community composition and seasonal patterns in 1994 at these sites were similar to those observed in 1979-80. Batophora abundance was greatest in summer; it was the dominant species in summer on the bay flat and canal wall. Laurencia abundance peaked in winter; it was the dominant species in winter on the canal wall. Acetabularia abundance was greatest in winter.

Rainfall in the 1994 wet season was well above average resulting in considerable freshwater flow into Florida Bay. This inflow lowered salinity substantially in much of Florida Bay for several months. At my sites salinity was 22-24 ppt from mid-October 1994 to mid-March 1995. Previously (1979-80, 1994 through August), I had never recorded salinity below 32 ppt. However, this extended period of lower salinity had little or no effect on these macrophyte assemblages. The macrophyte community in March 1995 was similar to that in March 1994 and March 1980.

Habitat Inventory and Change in Seagrass and Other Aquatic Beds in Florida Bay

Frank J. Sargent, Florida Department of Environmental Protection, Division of Marine Resources, Florida Marine Research Institute, 100 Eighth Avenue S.E., St. Petersburg, Florida 33701; Randolph L. Ferguson , Ford A Cross, NOAA/NMFS, Southeast Fisheries Science Center, Beaufort Laboratory, 101 Pivers Island Road, Beaufort, North Carolina 28516.

This research, cooperatively funded by NOAA's Coastal Change Analysis Program (C-CAP) and Florida Department of Environmental Protection (DEP), is generating geospatial data of benthic habitats in central and eastern Florida Bay from NOAA NOS tide coordinated metric quality aerial photographs. Source photographs are both contemporary (1991-1995) and historical (1950-1990). Analysis includes comprehensive contemporary habitat inventory and spatially limited recent and historical change detection. The work is being conducted in cooperation with NOAA, National Ocean Service (NOS) and the National Park Service, Everglades National Park. The work is a companion effort to the Florida Keys National Marine Sanctuary (FKNMS) Benthic Habitat Mapping Program. The Florida Bay research will provide information essential to assess recent and historical change and to guide efforts to manage and restore shallow water benthic habitats in Florida Bay. The project is scheduled for

http://www.aoml.noaa.gov/flbay/seag95.html (13 of 17)9/10/2007 2:32:42 PM Seagrass Ecology-1995 completion in FY97.

Inventory and change detection of seagrasses and other benthic habitats is combining the photogrammetric and benthic habitat expertise in NOAA and Florida. NOAA staff and cooperators include Greg Fromm, Coast and Geodetic Survey, Photogrammetry Branch, and Peter L. Grose, Chief, Data Management and Geographic Information Systems, Strategic Environmental Assessments Division, Office of Ocean Resources Conservation and Assessment. The goal of this research includes addition of the data to the C-CAP national resource spatial data base and the transfer of data conversion and thematic data processing technology to the State of Florida.

An aerial photographic mission for benthic habitats and shoreline delineation was conducted in the winter of 1991/92. The mission was limited by recurrent turbidity. To complete coverage of the study area and to allow for analysis of recent change for part of the study area, additional photography was acquired in April, 1995. The 1992 and 1995 photography plus historical photography from NOS complete the source data.

C-CAP funded James Fourqurean, Florida International University (FIU), to interpret benthic habitats consistent with the classification schemes developed for the (FKNMS) Benthic Habitat Mapping Program and for C-CAP. The FIU effort to interpret the 1991/92 photographs received logistical support from the Everglades National Park. That interpretation has been completed and is being quality assured by the Florida DEP, Florida Marine Research Institute (FMRI) for cartographic consistency prior to submission to NOS for georegistration and digitization at the end of this calendar year.

The protocol for interpretation, surface level signature verification and the classification system to be followed in the study were developed by C-CAP and FKNMS and have been integrated by FMRI to accomodate regional conditions and to meet both regional and national information needs. Metric quality photography (natural color, 1:48,000) was acquired with standard operating procedures for NOS photographic missions and C-CAP (Coastal Change Analysis Program (C-CAP): Guidance for Regional Implementation, NOAA Technical Report NMFS 123, April, 1995). Digital shoreline data critical to the proposed study are being generated by NOS.

The retrospective change analysis will be based on selected metric quality historical photography from 1950 through 1990. All interpretations of the historical photography are supported by contemporary aerial photographs and extensive surface level verification of contemporary aquatic bed signatures as described in the C-CAP guidance document. Interpretations of habitat polygons will be geopositioned by NOS in an analytical plotter, converted to ARC/INFO files using Standard Digital Data Exchange Format, and processed to a thematic inventory and change database. The horizontal accuracy for geopositioning (excludes habitat polygon interpretation error) is 3 meters.

Products will include photographs of central and eastern Florida Bay (1992 and 1995), digital geospatial data and hard copy maps of aquatic bed occurrence and change. The metric quality aerial photographs will be deposited in the NOAA photographic archive.

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Spatial data files will be available through the NOAA National Oceanographic Data Center and FMRI.

Spatial and Temporal Variations in Seagrass Biomass and Productivity Across Florida Bay

J.C. Zieman , Department of Environmental Sciences, University of Virginia, Clark Hall, Charlottesville VA 22903; James Fourqurean , Thomas Frankovich , SERP, Florida International University, Miami FL 33199.

The bay bottoms and banks of Florida Bay constitute one of the largest seagrass resources in north America. As such it has served as a major nursery and feeding ground for numerous organisms that are important commercially or are in the trophic web of important sportfish. The system has historically been dominated by turtle grass, Thalassia testudinum, which has high habitat values. Among the most important of these are its high productivity in areas with sufficient light, and the strong sediment stabilization offered by its dense rhizome and root mat, and by its dense canopy of leaves. Syringodium filiforme, Halodule wrightii, and Ruppia maritima also occur, but in less abundance than Thalassia, and moreconfined areas throughout the bay.

Since the fall of 1987, Florida Bay has experienced a major dieoff of Thalassia over large portions of Florida Bay. Initially the effects were confined to the immediate basins containing the originial dieoff patches, but by 1992 these effects had spread to hundreds of square miles outside of the ENP boundary. The primary downstream effects of the dieoff are large plumes of turbid and pigmented water, varying in density, size, and duration.

The recent distribution and abundance of seagrass in Florida Bay was mapped in the early 1980's (Zieman et al, 1989). The dominant pattern one of sparse seagrass in the northeastern bay increasing in density to the south and west. The highest densities and productivities were in the basins and on the banks of the western bay, roughly from Rabbit Key Basin westward.

Following the initial episodes of dieoff studies of plant and nutrient dynamics were done in the summer and fall of 1988. In 1989 a number of stations were established to determine the current and future state of Thalassia. Among the parameters measured are standing crop, biomass, areal productivity, turnover rate, shoot density and growth rate, leaf growth rate, and LAI. Initially stations were established in Rankin Lake, Rabbit Key Basin, Johnson Key Basin, Sunset Cove, and at Duck Key. Later stations were added at Sprigger Bank, Whipray Basin, and on the seaside off Tavernier Key. Monitoring rates have been from five to two times per year, depending on funding.

Analyses in progress relate the plant parameters described above to temperature, salinity, and seasonal factors. The pattern and response of Thalassia turnover rate (or specific productivity) is of primary

http://www.aoml.noaa.gov/flbay/seag95.html (15 of 17)9/10/2007 2:32:42 PM Seagrass Ecology-1995 importance, as it is normalized for plant biomass. This allows more direct comparison of the plant responses across the nearly 50 km gradient across Florida Bay. Standing crop routinely is 8-10 times greater at Spigger Bank and Rabbit Key Basin in the west than at Duck Key in the northeast, and can reach a 20x difference.

Primary Productivity and Standing Stock Estimates of Benthic, Epiphytic, Plankton, and Seagrass Communities of Florida Bay

Paul V. Zimba, Department of Fisheries and Aquatic Sciences, University of Florida .

As part of FMRI sponsored research on discoloration events in Florida Bay, field assessment of seagrass and microalgal standing stock has occurred on a bimonthly basis for over 15 months. This work is nearing completion, with interim reports due in November 1995, and a project summary report due in June 1996. Sites studied in this work include Rankin Bight (dominated by Thalassia testudinum and Halodule wrightii), Captain Key (monotypic Thalassia), and Sprigger Bank (dominant seagrass Syringodium, with Thalassia). Each site was analyzed for water column nutrient content (alkalinity, N, P, and Si), chlorophyll a, and physico-chemical conditions (salinity, temperature, pH, dissolved oxygen, and light penetrance). Standing stock was estimated using fixed point-transect methodology to collect seagrass biomass, partition epiphytes (as dry weight and chlorophyll a), and estimate benthic chlorophyll levels. For reference water column planktonic chlorophyll samples were also collected. Primary productivity was determined in situ using plexiglass chambers and a two hour incubation period (14C methodology). All productivity components were measured in the chambers simultaneously. Supporting data includes PAR measures made at least once during each incubation, HYDROLAB data (salinity, temperature, pH, and dissolved oxygen), as well as water column nutrient data (N,P, and Si) including alkalinity. Microalgal samples have been collected for cell identifications and enumerations, this data will not be presented comprehensively herein.

Primary productivity results for two representative sites ("pristine" - Captain Key and "impacted" - Rankin Bight) are presented in Figure 1. Significant correlations were observed between bottom irradiance (4 p spherical sensor) and rates of carbon uptake. Wind speeds greater than ca. 15 mph at Rankin Bight resuspend sediments and benthic microalgae (primarily pennate diatoms), causing a shift in bottom light to orange-yellow wavelengths. Increased turbidity at Captain Key (since Spring 1995) has reduced seagrass biomass, bare areas have been colonized by drift and benthic microalgal red and green species. Analysis of suspended particulate by x-ray diffraction methodology confirmed calcite as the dominant mineral present. Increased sediment productivity at Rankin Bight (up to 32 fold higher than initial conditions) has coincided with periods of increased light transmittance to sediments, lowered water column productivity, and declines in seagrass biomass. Seagrass productivity at Captain Key has declined from February 1995 to present.

Standing stock estimates of seagrass, benthic microalgae, plankton, and epiphytes were measured

http://www.aoml.noaa.gov/flbay/seag95.html (16 of 17)9/10/2007 2:32:42 PM Seagrass Ecology-1995 simultaneously to the productivity experiments. For comparative purposes, dry weight equivalents for each productivity component will be calculated using standard conversion factors. Preliminary data analyses suggest epiphytic biomass in terms of chlorophyll a exceeds 75 µg/seagrass shoot in Florida Bay, mean epiphytic biomass in the Indian River Lagoon by contrast is around 50 µg/shoot. This work will be completed as part of the November interim report.

Analysis of water column, epiphytic, and benthic microalgal samples for species composition and abundance are also required in this contract. Taxonomic composition of water column samples reveal at least two distinct plankton communities. The central interior Bay (Captain Key and Rankin Bight) have a mixed diatom/ cyanobacterial composition, whereas the more open water stations have algal assemblages more typical of continental shelf waters/Gulf waters. Typical species in Rankin Bight samples include the centric diatoms Cyclotella choctawhatcheena Prasad and unicellular Chaetoceros spp., along with epiphytic and benthic pennate diatoms from the genera Cocconeis, Mastogloia, and Amphora, as well as cyanobacteria from the genera Oscillatoria, Synechococcus, and Microcystis. On a biovolumetric basis, Rankin Bight is typically dominated by diatoms. The two western stations (Sprigger Bank and Sandy Key) are strongly influenced by offshore waters. Continental water intrusions entrain centric diatoms from the genera Rhizosolenia (e.g. R. calcar-avis, R. alata v. indica) and Chaetoceros spp. into Florida Bay, higher nutrient waters found within the Bay relative to shelf waters increase cell densities relative to offshore waters. Sediments are dominated by pennate diatoms from the genera Nitzschia, Pleurosigma, Amphora, Mastogloia, and Cocconeis. Epiphytic samples contain many of these same genera, with at least four other genera well represented. Potential results from these counts include canonical correspondence analyses using cell counts correlated with environmental conditions to develop a Florida Bay specific gradient model employing environmental measures made in the field. This model should then be tested by canonical discriminant analyses to identify similar patterns in the species and environmental data.

Mesocosm experiments currently underway include examination of altered light quality on seagrass photosynthetic efficiency, pigment composition, as well as spectral influences on the epiphytic microalgae. This work will be completed in late Fall, and would not be possible without support from Keys Marine Laboratory or FMRI personnel in Marathon, FL.

Last updated: 07/16/98 by: Monika Gurnée [email protected]

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Sedimentation & Paleoecology

1995 Abstracts

Natural and Anthropogenic Events Impacting Florida Bay, 1910 - 1994 Time Line

A. Y. Cantillo, NOAA/NOS/ORCA,Silver Spring, MD; L. Pikula, NOAA/Miami Regional Library, Miami, FL; J. Beattie , E. Collins , NOAA/Central Regional Library, Silver Spring, MD; K. Hale, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL; T. Schmidt, Everglades National Park Research Center, Homestead, FL.

Florida Bay is a coastal lagoon, on average less than 3 m deep, approximately 1,000 square miles in area, located between the South Florida mainland and the Florida Keys. In recent years, adverse environmental changes have been noted in the Bay. Currently, a multi-agency multi-year effort is underway to restore the ecosystem of South Florida, including that of Florida Bay. To assist in determining the Bay's former condition and to catalogue changes, events that may have affected or have occurred in the Bay are described, listed and graphically displayed in a common time scale. The time coverage begins in 1910 with construction activities along the Florida Keys, and in what later became the Everglades National Park. Included are global scale atmospheric, geological and astronomical phenomena such as El Niño events, volcanic eruptions and solar activity that may affect local weather. On local scales, documented are dieoffs of species such as seagrasses, sponges and fishes; environmental occurrences of algal blooms, coral reef degradation, fishery catch changes and soil subsidence; and human activities such as population increases, and construction. Awareness of the environmental importance of the Bay is documented in legislation affecting environmental regulations nationwide and in the Bay area; and environmental programs and studies performed currently and in the past by Federal, state, municipal, academic and civic organizations.

An Approach to the Retrospective Analyses of Salinity in Florida Bay Using Carbon and Oxygen Isotopes From Mollusk Shells

Robert B. Halley, Leanne M. Roulier, USGS 600 4th St. South , St. Petersburg, FL 33701.

Recurring hypersalinity in Florida Bay has raised questions about the possible influence of onshore

http://www.aoml.noaa.gov/flbay/sedi95.html (1 of 17)9/10/2007 2:32:43 PM Sedimentation & Paleoecology-1995 water management practices on salinity of the bay. The primary forcing factors of salinity in the bay are seasonal precipitation and evaporation which vary so widely that salinity changes are difficult to specifically characterize. The fossil record of the bay offers the potential for providing a salinity record with resolution of decades, or better, during the past century and a half under natural conditions. To test the hypothesis that older shells can be used to characterize salinity before the turn of the century, we have used carbon and oxygen isotope ratios (δ13C and δ18O) of mollusk shells from surface sediment as a proxy for physical and chemical water characteristics.

A four-inch diameter core was taken in each of five sub-basins in Florida Bay. These sub-basins are located in Long Sound, Buttonwood Sound, Alligator Bay, Whipray Basin, and Old Dan Bank northwest of Long Key. The selected sub-basins range from being strongly influenced by freshwater runoff (Long Sound) to being dominated by Gulf of Mexico and Atlantic Ocean water (Long Key) . In each sub-basin except Long Sound and Alligator Bay a core was taken in scattered turtle grass (Thalassia testudinum) growths to obtain organisms that grow attached to the grass. Turtle grass was not present in Long Sound and Alligator Bay but other grasses were present that might serve as substrate for many organisms commonly attached to Thalassia testudinum.

The coarse fraction of the sediment from the upper 10 cm of each core was washed and separated into two size fractions: 425 um - 1 mm and > 1 mm. Working primarily with the 425 um - 1 mm fraction, commonly occurring species were identified and separated from each sample. Seven species of mollusks, two species of foraminifera, and a serpulid worm were identified in most samples. On average, 15 individuals of each species were selected for analyses. If at least three individuals could not be found in a sample, the species was considered absent. Individual shells, or several portions of an individual, were crushed using a mortar and pestle, split and then analyzed in the USGS mass spectrometry laboratory in Denver, CO. More than 700 analyses allow the evaluation of species that are best for retrospective analyses and provides for the statistical characterization of the samples from each sub-basin.

Grouping the data by location (Figure 1) shows that each sub-basin has distinctive characteristics. Mollusks from near Long Key and Long Sound have mutually exclusive δ18O and δ13C values that compose end-member distributions. The widest range in δ18O values is seen in Long Sound where the most positive δ18O values reflect greater net evaporation and the more negative δ18O values occur in response to increased fresh-water input. In contrast, more "normal marine" values are maintained near Long Key where variations in temperature and salinity and thus δ18O and δ13C are relatively small due to the more open exchange with the Gulf of Mexico and Atlantic Ocean. Moving toward the exterior of the bay, from Long Sound to Long Key, the intermediate sub-basins including Buttonwood Sound, Alligator Bay and Whipray Basin exhibit quite a bit of overlap, but show progressively more marine-like isotopic characteristics. The degree to which all of these areas are influenced by evaporation and fresh water may also be related to the slope defined by the regression through data for each sub-basin. These results indicate that it is conceivable to evaluate salinity based on mollusk shell isotopic composition, even though salinity variations in Florida Bay are complex and not as quantitatively well-defined as in other coastal settings. It follows that the isotopic analyses of mollusks from successive samples taken

http://www.aoml.noaa.gov/flbay/sedi95.html (2 of 17)9/10/2007 2:32:43 PM Sedimentation & Paleoecology-1995 down carefully dated cores will provide a measure of natural, long-term salinity change in Florida Bay.

Florida Bay Salinity: Fragile Links Between Sediments, Sea Level, and Onshore Water Management

Halley, R. B. , Shinn, E. A. , USGS, St. Petersburg, FL 33701; Holmes, C. , USGS, Denver, CO 80225; Robbins, J. A. , NOAA, GLERL, Ann Arbor, MI 48105; Bothner, M. K. , USGS, Woods Hole, MA 02543; Rudnick, D. T. , South Florida Water Management District, West Palm Beach, FL 33406 .

Recent rapid ecological change in Florida Bay is widely believed to result from long-term changes in water quality, particularly salinity and nutrients, that have been influenced by onshore flood control and drainage projects completed during the last century. Overlooked, however, is the natural rise of sea level (30 cm since 1850) and the increased depth of Florida Bay. Because sediment production rates are insufficient to compensate for the added volume of the bay, more marine water covers the bay than did a century ago. Therefore, even if the same amount of freshwater had been delivered to Florida Bay, salinity would have increased simply because there is more marine water to dilute.

Florida Bay is a shallow lagoon subdivided by mudbanks into several dozen subbasins, that vary from nearly normal marine to estuarine. Poorly documented transport processes erode fine-grained sediment from subbasins and leave many sediment starved (floored by exposed Pleistocene limestone). Mudbanks are eroding on their northern and eastern slopes, probably in response to winter storms. Newly produced, as well as older, eroded sediment preferentially accumulates in the lee and on top of mudbanks at rates as great as 1-4 cm/yr, as indicated by 210Pb and 222Ra analyses. These observations suggest the elevations of banktops are maintained during sea-level rise by a balance of erosion and deposition resulting in overall buildup and migration. Mudbank segmentation and restriction of the bay have outpaced sea-level rise and have allowed subbasins to remain highly variable in water quality. Thus, two natural processes, sea-level rise and sedimentation, require evaluation in order to understand ecosystem- scale change in Florida Bay and to plan related onshore restoration activities.

The Hydrology and Geochemistry of Mangrove Mud-Islands in Florida Bay

Philip A. Kramer, Peter K. Swart , Marine Geology and Geophysics, RSMAS, University of Miami, Miami, Fl 33149; T.C. Juster , H.L.Vacher, Department of Geology, University of South Florida, Tampa, Fl 33620.

Over 230 small mangrove islands are found along the mudbanks and basins of Florida Bay. They serve

http://www.aoml.noaa.gov/flbay/sedi95.html (3 of 17)9/10/2007 2:32:43 PM Sedimentation & Paleoecology-1995 an important role in the overall trophic dynamics of the Bay, as well as provide critical nesting and foraging habitat for a variety of birds, reptiles, and aquatic invertebrates. While it has long been recognized that these environments are saline to hypersaline, little is known about their flooding frequency, hydroperiod, rates of horizontal and vertical porewater movement, or porewater geochemistry.

This study has examined the hydrological and physical environmental conditions which lead to the formation of hypersaline pore waters on these islands. The overall goals of this study were three fold: 1) understand the basic surface hydrology and rates of water flux through the islands 2) to characterize the spacial and seasonal variability of the early diagenetic processes, and 3) to document the controls on the dissolution and precipitation of carbonate minerals in these high ionic strength sediments. While largely motivated by geochemical interest, this study has shed light on many of the important hydrogeological processes occurring on these islands which directly impacts the vegetation, birds, and aquatic invertebrates inhabiting them.

Two islands were examined in detail for this study: Cluett Key (located in western Florida Bay), and Jimmy Key (located in eastern-central Florida Bay). These two islands were chosen because of major differences in their physiographic characteristics, sedimentology, developmental history, and porewater chemistry. Each appears to represent the two extremes of island-types within the Bay.

Field logistics and the unconsolidated properties of the sediments necessitated using a variety of hydrological and geochemical sampling methods. Both islands were extensively instrumented in Spring, 1993 with pressure transducers, rain gauges, and sampling wells. The pressure transducers were placed in vertical nests along a transect 50-75 meters long and surveyed to a common datum using sight and transit. Water levels in the ponds, adjacent bay, and underlying limestone were also monitored using pressure transducers. All instruments were connected to remote data loggers. Sampling wells (1 1/4" diameter pvc pipes) were placed in nests of 5 (depths 25, 50, 100, 150, 200 cm) adjacent to nests of pressure transducers to allow rapid porewater collection. The islands were visited every other month beginning in Spring 1993 to July 1994. On each visit, data was downloaded, wells were pumped and sampled, and cores were taken. Water samples were analyzed for alkalinity, pH, salinity, and cations (Ca ++, Mg++, Sr++, K+) and anions (Cl-, SO4--). In addition, tritium (half life 12.43 years) and δ18O was measured in selected water samples. Cores were squeezed and analyzed as above, as well as for H2S, bromide, ammonia, and phosphate. Sediments examined for water content, permeability, porosity, and mineralogy.

The islands were flooded by bay water during the new and full moon spring tides that arrive every two weeks. Annual changes in Florida Bay water levels, short term wind effects, and the elevation of an island's levee are the major controls on the flooding frequency. During the study period, mean water levels in Florida Bay were about 20 cm higher in the fall than in the spring. This resulted in a much higher flooding frequency during the fall months. High water levels were maintained in the ponds through most of the year, dropping only during spring and early summer, when the interior ponds dried out completely. The groundwater table dropped substantially during these dry periods. On Cluett Key, the water table fell by as much as 50 cm below the pond surface forming large unsaturated zones. On

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Jimmy Key the groundwater table only dropped 10 cm below the pond floor due to the lower amount of exposure those sediments endured.

Rainfall mainly affected the surface waters during periods of low flooding frequency and limited tidal exchange (February through July). The shallow depth of the island ponds, coupled with the large seasonal changes in flooding frequency, rainfall, and rates of evaporation allow for rapid changes in surface water salinities. Highest salinities coincide with times when the evaporation- to- recharge deficit is at it's peek during the late spring and summer. A decrease in the late summer and early fall occurs when heavy rains begin, and Florida Bay water levels rise so that frequent flooding is assured.

The limestone groundwater beneath Cluett Key is hydraulically "linked" to the surrounding Florida Bay water. The movement of surface and porewaters on the islands are influenced by this hydraulic link. During the wet season a net downward gradient of .1 exists between the interior ponds and the adjacent bay, after short term tidal variations are subtracted. This substantial head gradient can potentially move water downward through island sediments during this time of year. In contrast during the spring, the groundwater levels in the islands drops below that of the adjacent bay and conditions for upward flow combined with upwards evaporative capillary movement exist. The extent of movement is limited by the low hydraulic conductivity of the sediments, which decreases from 10-2 m-day-1 to 10-4 m-day-1 at greater depths due to compaction and root void filling as sediments are buried. Horizontal movement is insignificant due to the vertical nature of many of macropores and root voids, and the small (<30 cm) topographic gradients of the island terrain. Tritium measurements confirm this general vertical movement, and indicate that the porewaters on these islands are all less than 40 years old.

Large temporal changes in soilwater salinity were observed in the upper 50 cm of both islands, with profiles "hinging" back and forth. The highest salinities occurred during dry periods and were measured in excess of 250‰. The lowest salinities occurred during frequent flooding and after heavy rains diluted surface waters. These salinity changes are consistent with surface soils undergoing seasonal evaporation and dilution by flood waters and rainfall. The depth to which these short term changes are propagated coincides with the average depth that the water table falls in a given area during dry out.

Below 50 cm, pore water salinity variations become damped out and begin to approach a constant value representative of the time-averaged mean of the changes occurring in the soilwaters above. In nearly all profiles examined, this time-averaged maximum salinity occurred between 75 and 150 cm beneath the surface. Concentrations of salt in soilwaters gradually decrease to the limestone contact, 1 to 2 meters below. No significant changes in pore water salinity at these greater depths were recorded over the study period.

The chemical changes in porewaters reflect both microbial and early diagenetic processes. The major driving force in determining the direction and magnitude of the chemical changes is the amount of exposure the sediments receive, and the input and types of input of organic carbon to the sediments. These chemical pathways generally correlate to processes occurring within distinct vegetation zones. In the mangrove fringe there are high inputs of leaf detritus, and frequent flooding of the soils. This results

http://www.aoml.noaa.gov/flbay/sedi95.html (5 of 17)9/10/2007 2:32:43 PM Sedimentation & Paleoecology-1995 in extensive sulfate reduction within the upper sediments. This sulfate reduction is coupled to moderate amounts of high magnesium calcite and aragonite dissolution, and limited amounts of calcite/dolomite precipitation. In the high hammock zone, extensive dissolution was also documented, but through a different process of organic matter oxidation. Meteoric water and salts derived from sea-spay collects in the upper sediments and initially dissolves aragonite and high magnesium calcite as it comes into equilibrium with the sediments. Oxidation of organic carbon using oxygen, nitrate, and sulfate within the root zone of the shrubs and trees elevates the pCO2 which further promotes dissolution of aragonite and High magnesium calcite. Some of the highest rates of carbonate dissolution occur in the high hammock zones of the islands. In the ponded interiors, pore waters have much higher salinities. Gypsum formation occurs in the most exposed sediments, but that very little sulfate reduction or pyrite formation was found.

This study has demonstrated for the first time the mechanisms which control the flooding and hydrology of the mangrove islands which play an integral part of the ecology of Florida Bay. These studies reveal that the high salinities in the islands are unrelated to the salinity in the bay, but are controlled by the height of the levee surrounding the island and the amount of evaporation on the island. In future work we propose to study the hydrological connections between adjacent basins and implications that these connections may have on the geochemical flux from the sediments.

Remote Sensing of Water Turbidity and Sedimentation in Florida Bay

Richard P. Stumpf, US Geological Survey, Center for Coastal Geology, St. Petersburg FL 33701.

Water turbidity produced by resuspension events have a potentially significant impact on water quality and various bottom communities in Florida Bay. We are using satellite imagery in conjunction with field observations to describ the frequency and extent of turbidity events.

Several types of satellite will be examined in the course of the project. The primary source will be AVHRR data, which is available almost daily at 1 km pixel size. Landsat data, at 80 m, is available sporadically from 1973, Landsat TM at 30m from 1984; and ocean color sensors, such as SeaWiFS and OCTS are anticipated for launch in 1996. Imagery will be processed to water reflectance by correcting for atmospheric affects and sun angle, and removing bottom albedo. Field observations will be used to establish diffuse attenuation and total suspended solids.

At present, AVHRR imagery is being evaluated, about 400 suitable scenes (of over 1800 data sets) are in hand and processed for aerosols and sun angle from December 1989 to the present. The AVHRR data sets have also been processed for sea surface temperature.

Meteorological observations from NOAA CMAN stations are also being examined with the imagery. The impact of the cold fronts on water clarity is evident in the Bay. Recent imagery is being made

http://www.aoml.noaa.gov/flbay/sedi95.html (6 of 17)9/10/2007 2:32:43 PM Sedimentation & Paleoecology-1995 available in preliminary form on the Internet for use in Florida Bay studies. The effort over the next year will be establishing light attenuation coefficients from the satellite imagery and incorporation of Landsat data to look at some early time periods.

A History of Salinity and Eutrophication in Florida Bay Using Stable Oxygen and Carbon Isotopes From Scleractinian Corals

Peter K. Swart, University of Miami, 4600 Rickenbacker Causeway, Miami FL 33149; Genny Healy, MGG/RSMAS, University of Miami, 4600 Rickenbacker Causeway, Miami FL 33149; Richard E. Dodge, Nova Southeastern University, Oceanographic Center, 8000 North Ocean Dr., Dania FL 33004.

In order to investigate historical variations in the water quality of Florida Bay we have utilized changes in the oxygen and carbon isotopic composition of the skeletons of scleractinian corals growing in Florida Bay. The oxygen isotopic ratio (18O/ 16O) of the coral skeleton records changes in salinity and temperature, while the carbon isotopic ratio (13C/ 12C) indicates the overall physiological condition of the coral as well as the ambient ratio in the dissolved inorganic carbon (DIC) of the prevailing water. Oxygen and carbon isotopic ratios are usually reported in the conventional δ notation as parts per thousand (‰) relative to an international standard (PDB).

In our studies we are using two different species of corals, Solenastrea bournoni and Siderastrea radians. The specimens of S. bournoni we are using are large (120 to 150 years in age) and are as far as we know restricted to Lignumvitae basin. These corals were originally cored in 1986 and their growth rates and fluorescence descibed by Hudson et al. (1989) and Smith et al. (1989). The corals were cored again in 1993 and 1994 by our group and the δ13C and δ18O have been correlated with recent high resolution salinity, temperature, and nutrient data obtained from Florida Bay. In order to extend our interpretations to other basins where the Solenastrea corals are not present, we are using specimens of the species Siderastrea radians, a small grapefruit sized coral which grows to an age of between 20 to 40 years.

We have correlated changes in the δ18O of the coral skeleton of Solenastrea with salinity over the past 30 years and developed a statistically significant association between these two variables; the skeletal δ18O increases with increasing salinity. Based on an analysis of the δ18O of the Solenastrea bournoni in Lignumvitae Basin we have concluded that while there has been no long term increase in salinity in this basin of Florida Bay over the past 160 years (Figure 1), there is an increase in δ18O coincident by the construction of the Florida East Coast Railway from Miami to Key West between 1905 and 1912. The construction of the railway resulted in the restriction of the exchange of water between the Florida reef tract and the Gulf of Mexico causing Lignumvitae Basin to become slightly more saline. From 1910 to 1986 there has been no obvious increase in the skeletal δ18O and therefore we conclude there has been no increase in salinity. Large changes also occurred in the skeletal δ13C values coincident with railway construction. After 1910 the skeleton contained more 12C, a phenomenon which is related to the

http://www.aoml.noaa.gov/flbay/sedi95.html (7 of 17)9/10/2007 2:32:43 PM Sedimentation & Paleoecology-1995 increased contribution of the products of the decay of organic material to the dissolved inorganic carbon pool . We suggest that the railway construction process, which restricted the exchange of water, also allowed more organic material to be retained within Florida Bay. The organic material eventually degrades to CO2 producing a characteristic signature in the water column.

Natural events also appear to have influenced the water in the Bay. Between 1912 and 1948, frequent hurricanes had the effect of increasing exchange of water between the Bay and reef tract and removing large quantities of organic rich sediments (Figure 2). However, since 1948 the number of hurricanes affecting the area has decreased and the products of the oxidation of organic material have been increasingly retained within the basin promoting the initiation of eutrophic conditions. The interpretation of this work have been accepted for publication (Swart et al., In Press).

In order to better calibrate changes in the water quality of Florida Bay to the skeletal coral record, we have used the high resolution environmental data collected by the Everglades National Park and Florida International University in conjunction with their water quality monitoring program over the past several years. As data on the δ18O and δ13C of Florida Bay water has not been available, we have also started to collect this information. These data combined with high resolution sampling of the coral skeleton have allowed us to improve the correlations between salinity and skeletal δ18O. Based on the new calibration and an independent indicator of temperature, such as the Sr/Ca ratio of the coral skeleton, we feel that it should be possible to obtain an unambiguous record of salinity in Lignumvitae Basin for the past 160 years.

One criticism of our interpretation of the data from Lignumvitae Basin has been that the results from this basin might not be representative of other portions of the Bay. In order to assess how the record in Lignumvitae Basin relates to other basins, we are using the small coral Siderastrea radians. This coral appears to be widespread throughout the bay growing in areas with rocky bottoms. Some of these specimens can be up to 30-40 years in age. Our first analyses of this coral show good agreement between the δ18O and the salinity of the water.

References

Hudson, H.D., Powell, J.V.D, Robblee, M.B. and Smith, T.J., 1989. A 107-year-old coral from Florida Bay: barometer of natural and man-induced catastrophes, Bull Mar. Sci., 44:283-291.

Smith T.J., Hudson, JH, Robblee, M.B., Powell, G.V.N., and Isdale, P.J., 1989. Freshwater flow from the Everglades to Florida Bay: A historical reconstruction based on fluorescent banding in the coral Solenastrea bournoni, Bull. Mar. Sci., 44:274-282.

Swart, P.K. Healy, G. Richard, Dodge,R.E. Kramer ,P. Hudson,H. Halley, R. & Robblee , M. (In Press) The Stable Oxygen and Carbon Isotopic Record from a Coral Growing in Florida Bay: A 160 Year Record of Climatic and Anthropogenic Influence, Palaeo, Palaeo, Palaeo

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Documenting the Styles of Sedimentation and Contained HIstorical Sedimentary Record in Shallow Marine Environments in and Adjacent to Florida Bay, South Florida

H.R. Wanless, Dept. Geological Sciences, University of Miami; T.A. Nelsen, AMOL, NOAA; L.P. Tedesco, Dept. Geology, Indiana/Purdue University at Indianapolis; J. H.Trefry , Dept. Oceanography, Florida Institute of Technology; P.L. Blackwelder , J.A. Risi, Rosenstiel School of Marine and Atmospheric Science, University of Miami.

The investigators are involved in two projects in and proximal to Florida Bay. One is to document the fate of hurricane deposits and evolution of hurricane impacted environments. The second is to assess the viability of using sedimentologic, geochemical and paleoecological records in layered sediment sequences to document historical changes in the environments influencing Florida Bay.

The project studying fate of hurricane deposits is in its second of three years of funding and involves sampling strata from historical hurricanes (principally Andrew, Betsy, Donna, and the Labor Day Hurricane of 1935), documenting changes in deposited storm layers, substrate subsidence, and recolonization or evolution of biotic communities. We are focusing on Biscayne Bay, Florida Bay and the Everglades west coast north to Chatham River. Over 150 cores have been collected to characterize Andrew, Betsy, Donna and the Hurricane of 1935. Aerial photographs from 1927 to present have been analyzed.

With respect to Florida Bay, a most important finding of this study is the recognition that hurricane- destroyed mangrove swamps may undergo a period of rapid substrate subsidence (we are measuring 2-4 cm per year following Andrew). Large volumes of detrital and dissolved organics are being released from the decaying mangrove swamp substrate. On the west coast, some of this released organic detritus has formed thick (0.5-1.5 meters in 3 years) post-event deposits in the inner bays and in side channels. Much is being carried seaward to the offshore environment. Winter storm resuspension and transport processes are moving these offshore particulates southward into northwest Florida Bay and southward through the Keys to the reef tract.

This post-event redistribution is still occurring for mangrove swamps damaged by the Great Labor Day Hurricane of 1935 and Hurricane Donna (1960). The large areas of coastal and interior mangrove forest on northern Cape Sable damaged by these storms have not recovered. Rather, as the peat substrate has decayed, the surface has subsided into the lower intertidal zone where burrow excavation, grazing and tidal processes are completing the transfer of the storm-destroyed mangrove swamp to the subtidal. Large volumes of detrital and dissolved organics are still episodically discharged from this degrading environment.

The second study, using layered sedimentary sequences for paleoenvironmental reconstruction, is

http://www.aoml.noaa.gov/flbay/sedi95.html (9 of 17)9/10/2007 2:32:43 PM Sedimentation & Paleoecology-1995 focusing on finding meaningful stratified sediment sequences which contain an interpretable historical record. Most accumulating sediment sequences are formed layer by layer. This stratification (layering) is preserved in the shallow marine environments of south Florida where environmental conditions inhibit bioturbation. The stratified records, however, vary with respect to continuity of record, persistence of sediment deposition, local reworking, and presence/absence of erosional hiatuses. The nature of the sediment-biotic-geochemical record is dependent on the style of sediment deposition in the area. Six styles are recognized.

(1) Daily Sediment Deposition. A few areas receive significant sediment on a day to day basis and accumulate a detailed sediment record, though short lived because of rapid sediment buildup. (2) Winter Storm Deposition. Some deltas, banks and isolated depressions receive thin sediment laminae from episodic winter storms and tropical storms. Supratidal levees and berms receive depositional laminae from certain of the winter storm and tropical storm events. (3) Hurricane Deposition. Hurricane events produce a significant sediment layer across much of the affected subtidal and supratidal environments. Layers vary in thickness from less than one mm to greater than one meter. (4) Post Event Deposition. Major hurricanes and major mangrove or seagrass dieoffs may initiate a phase of sediment reworking of material both from unstable areas and released from destabilized bottoms. Redistribution of this sediment results in accumulation of thick deposits in sediment sinks. Post Andrew sediment deposition is greater than 1.5 meters in a few areas. This post event redistribution may last a few years or decades, depending on the nature of the environmental disturbance. (5) Autochthonous Biogenic Sediment Deposition. Subtidal algal mats, Halimeda opuntia banks, and coral-coralline algae layers rarely preserve in situ. Supratidal mats have higher preservation potential. Seagrass recolonization can produce distinct epifaunal and infaunal communities that preserve in situ. (6) Allochthonous Biogenic-influenced Sediment Deposition. Seagrasses, algal mats, and scum mats modify the bottom energy, cohesiveness and stability. They provide conditions for deposition or stabilization of sediment that would normally not be deposited or retained.

These different styles of sedimentation have different sediment textures, fabrics, constituent composition and type of sedimentary structure(s). It is imperative that the style(s) of sediment deposition be distinguished in sequences being used for paleoenvironmental reconstruction as each records the local and regional physical, biotic and chemical environmental history differently. As many styles of sedimentation are not continuous through time or space, it is generally not meaningful to project average rates of sediment accumulation.

Different styles of sedimentation have very different rates and continuity of sedimentation. It is critical to accurately define the style or styles of sedimentation within a sequence before evaluating rates of sedimentation and the significance of geochemical and paleontological studies therein.

Other aspects must also be resolved in using sediment sequences for detailed paleo-environmental analysis. These include: physical and biogenic mixing, selective deposition or erosion, selective dissolution based on variations in mineralogy and skeletal microstructure, deep excavation and infill structures, biotic changes resulting from local substrate changes, and apparent chemical changes related to differing texture or constituent composition.

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Despite the potential pitfalls, fine-scale analysis of shallow marine sediment sequences provide an unequaled potential to reconstruct detailed local and regional hydrologic and paleoenvironmental history along a continuum of environments from fresh to marine.

During the first year of funding, we have used stratified sequences from four sites to evaluate the potential for detailed dating and paleoenvironmental reconstruction. These cores are from areas adjacent to Florida Bay that influence or reflect the environments of Florida Bay. Three core sites are on a gradient from the mouth of Shark River Slough (mouth of Avocado Creek) through lower Shark River (a laminated filled bay sequence in adjacent Whitewater Bay) to Ponce de Leon Bay (laminated bank in the northeastern sector). This transect has the potential to represent the changing influence of discharge from Shark River Slough to the adjacent marine environment. A fourth layered sediment sequence site in northwestern Coot Bay has provided an opportunity to evaluate how the sediment sequence has recorded known historical changes and influences (opening and closing of Coot Bay Canal connection with Florida Bay; Hurricane of 1935 and 1960).

Analyses of cores has included, style of stratification, degree and type of burrowing, constituent composition and texture, visual erosion or discontinuity surfaces; x-ray and color enhanced photography of cores; radiometric dating by 210Pb, 137Cs, and excess 228Th; analysis for Al, Cu, Hg, Pb, Zn, organic N, organic C, P; evaluation of contained pollen contained molluscs, foraminifera, arenaceous foraminifera, octracods, diatoms and other skeletal grains and fragments. Sampling for this first (reconnaissance) year was at 2-5 cm intervals spaced through the cores to look for presence and trends of the above listed components.

In the layered cores selected and analyzed, we have 80-120 cm thick sequences that record environmental history from about 1850-1900 to the present. All cores record a progressive upwards increase in Hg and Hg/Al, with the dramatic increase occurring in the 1940's. There is a progressive decrease in Hg from the mouth of Shark River Slough seaward to Ponce de Leon Bay. Coot Bay contains high levels of Hg and Hg/Al. This indicates an aerosol source for the pollutant, as Coot Bay is not in the main freshwater transport pathway from Shark River Slough.

Rapidly deposited storm and post-storm layers, burrowing, and style of sedimentation all affect the vertical radiometric, geochemical, and paleontologic profiles in the cores analyzed. Rates of sedimentation are not uniform in the sequences.

For year two, we are initiating a detailed analysis of layered sediment sequences from lower Shark River (bay fill in adjacent Whitewater Bay), northwestern Coot Bay, and First National Bank area in northwestern Florida Bay. We consider the approaches of these demonstration projects to have opened the door for future detailed paleoenvironmental reconstruction throughout Florida Bay and adjacent environments.

http://www.aoml.noaa.gov/flbay/sedi95.html (11 of 17)9/10/2007 2:32:43 PM Sedimentation & Paleoecology-1995 Florida Bay Ecosystem: Measuring Historical Change

G. Lynn Wingard, T.M. Cronin , D.A. Willard , S.E. Ishman , L.E. Edwards , C. Holmes , S.D. Weedman , U.S. Geological Survey, Reston, VA.

Recent negative trends have been observed in the ecosystem of Florida Bay, including algal blooms, seagrass die-offs, and declining numbers or shellfish, adversely affecting the fishing and tourist industries. Many theories of cause and effect exist to explain the adverse trends, but these theories have not been scientifically tested. Prior to finalizing plans for ecosystem restoration, the relative roles of human activities versus natural ecosystem variations need to be established. This project addresses this need by focusing on two primary goals. First, to determine the characteristics of the ecosystem prior to significant human alteration, including the natural range of variation in the system; this establishes the baseline for restoration. Second, to establish the extent, range, and timing of changes to the ecosystem over approximately the last 150 years and to determine if these changes correlate to human alteration, meteorological patterns, or a combination of factors. In addition, data on recovery times of certain components of the ecosystem will be obtained allowing biologists to estimate responses to proposed restoration efforts. This project is planned as a five year study, to be completed in 1999.

This project is one segment in a group of coordinated USGS projects examining the biota, geochronology, geochemistry, sedimentology, and hydrology of southern Florida, Florida Bay and the surrounding areas. Data are being compiled from terrestrial, marine, and freshwater environments in onshore and offshore sites in order to reconstruct the ecosystem history for the entire region over the last 150 years.

Methods: In cooperation with other USGS projects, and other state and federal agencies, a series of shallow piston cores (~1-2 m) have been collected in the central and northeastern areas of Florida Bay. The cores are x-rayed and examined to determine the degree and extent of sediment disruption. Cores that appear to contain relatively undisturbed sediments are submitted for 210Pb analysis to determine the age and degree of disruption of the sediments. An independent support for the age model is obtained by analysis of the pollen in the core; key introduced species include Casuarina, Schinus, and Melaleuca.

Cores that have a good stratigraphic record are sampled at closely spaced intervals (2 cm) for all macro- and micro-fauna and flora present. The primary biota analyzed are 1) benthic foraminifera, 2) ostracodes, 3) mollusks, 4) dinoflagellate cysts, 5) pollen and macro-plant material. The faunal and floral groups are compared by means of quantitative down-core assemblage diagrams. Determinations of salinity, bottom conditions, nutrient supply and various other physical chemical parameters of the environment are made for each sample based on the fauna and flora present.

Examination of the diversity and distribution of the fauna and flora over time allows us to infer the nature and extent of changes that have occurred in the ecosystem. In the marine environment, benthic foraminifera and ostracodes are used to suggest changes in salinity and substrate; micromollusks indicate substrate changes and general changes in salinity patterns; dinoflagellate cysts may indicate

http://www.aoml.noaa.gov/flbay/sedi95.html (12 of 17)9/10/2007 2:32:43 PM Sedimentation & Paleoecology-1995 algal blooms and current patterns; pollen reflects the composition of onshore vegetation, therefore providing an indication of regional changes, such as climate, hydroperiod or nutrient supply.

Data from all cores are being integrated to search for regional patterns of change in diversity and distribution of the fauna and flora; data from Florida Bay will be correlated to data obtained in the corresponding USGS onshore ecosystem history project. The integrated data set will be analyzed to see if detected changes in biota correlate to alterations in physical parameters and/or historic records of human-induced modifications of the environment.

In addition, modern core-top living assemblages are being collected twice a year (in the wet and dry seasons), over a period of several years, from the central and northeastern portions of the bay, in order to provide data on seasonality, habitat distribution, and preferred substrates of the living biota for interpretation of the down-core assemblages.

Preliminary Results: Two shallow cores have been examined to date: 1) Bob Allen #6A Core (172 cm total depth), located on a grass covered mud bank near the southern end of the Bob Allen Keys; 2) Taylor Creek Core T-24 (90 cm total depth), located near the mouth of Little Madeira Bay. The age model developed using 210Pb established a 1.1 cm/year sedimentation rate for the Bob Allen #6A core; the ages discussed below are estimates based on that rate.

The Bob Allen #6A core can be divided into five zones based on the benthic fauna. The ostracodes, mollusks, and benthic foraminifera in the lower portion of the core (172-135 cm; ~1850-~1890) show moderate diversity and abundance; they indicate that the salinity ranged from 20-30 ppt and the subaquatic vegetation was present in moderate amounts. The dinoflagellate cysts were low in abundance and the terrestrial vegetation, as indicated by the pollen, was pine-dominated upland forests. The portion of the core from 135-75 cm (~1890-~1930) is characterized by a very low diversity, low abundance, benthic faunal assemblage dominated by sand dwellers; subaquatic vegetation was low to absent, and the salinities ranged from 15-25 ppt. In contrast, dinoflagellate cysts were relatively abundant in this portion of the core, and the assemblage was dominated by one species, Polysphaeridium zoharyi. The terrestrial vegetation began to shift to typical wetlands species, with more salt-marsh, slough, and hardwood pollen present. All five biotic elements examined show corresponding changes at approximately the 135 cm and 75 cm sections of the core.

Above 75 cm in the Bob Allen #6A core a great deal of fluctuation occurs within the benthic fauna. This portion of the core is divided into three zones: 75-35 cm (~1930-~1970); 35-10 cm (~1970-~1985); and 10-0 cm (~1985 to the present). The 75-35 cm and 10-0 cm zones are characterized by moderate to high benthic faunal diversity and abundance, and low dinoflagellate cyst abundance. The benthic fauna indicate a period of extreme fluctuations in salinity, ranging from 20->50 ppt, and abundant subaquatic vegetation. The 35-10 cm zone is distinguished by a return to lower diversity and abundance for the benthic fauna, and low to moderate abundance for the dinoflagellate cysts. The salinities in this portion of the core appear more stable, fluctuating between 15-30 ppt, and the subaquatic vegetation was low. The pollen for the upper portion of the core, from 75-0 cm indicates greater abundances of onshore

http://www.aoml.noaa.gov/flbay/sedi95.html (13 of 17)9/10/2007 2:32:43 PM Sedimentation & Paleoecology-1995 wetlands environments, dominated by hardwoods, mangroves and buttonwoods.

The benthic fauna seen in the upper 60 cm in the Taylor Creek T-24 core show the same kinds of fluctuations as those seen in the upper 75 cm of the Bob Allen #6a core. The dinoflagellate cysts show a significant increase in the dominance of Polysphaeridium zoharyi at 75 cm in the Taylor Creek T-24 core, which may correspond to the increase seen at ~ 75 cm in the Bob Allen #6a core (although the Taylor Creek T-24 core has a higher sedimentation rate). Taylor Creek T-24 core has approximately 20% more Polysphaeridium zoharyi than Bob Allen #6a throughout the core; this is consistent with the more restricted marine setting of Little Madeira Bay. The pollen record for Taylor Creek T-24 shows more subtle changes in the onshore terrestrial environment, primarily because of its closer proximity to land, but the general patterns are the same. The basal portion of the core (90-80 cm) indicates a pine- dominated upland, and above 80 cm wetland vegetation becomes more abundant.

Our results indicate that major environmental changes occurred in the Florida Bay and Everglades ecosystems over the last 150 years. Periods of decreased salinity correspond to intervals of decreased subaquatic vegetation, lower benthic faunal diversity, and lower benthic faunal abundance. Periods of increased salinity correspond to intervals of increased subaquatic vegetation, higher benthic faunal diversity, and higher benthic faunal abundance. The pollen and dinoflagellate cyst records show that changes in the terrestrial habitat and the pelagic realm are roughly synchronous to the marine benthic faunal record. This apparent synchroneity between the marine and terrestrial realm implies changes occurred in parameters that affect both habitats. Rainfall and/or human-altered hydroperiods may be possible explanations for the changes seen. Presently, there is no evidence of hypersalinity in Florida Bay prior to ~ 1930. The fluctuating salinities and periods of hypersalinity that we see are consistent with controlled discharge through the canal system and inconsistent with natural sheet flow.

Future Work: Analysis of cores and samples collected to date will be completed, and monitoring of the modern environment for our core-top data base will continue. In addition, we hope to begin geochemical analyses of the shell material. Initial efforts have been concentrated in the northern and eastern portions of the bay, the areas presumed to be most impacted, but as patterns and trends begin to emerge, we plan to continue sampling along rough transects moving west and south through the Bay. Coordination with other USGS projects focused on terrestrial biota, geochronology, geochemistry, sedimentology, and hydrology should enable reconstruction of the regional ecosystem over the last 150 years by the time the project is terminated.

Paleoecology of the Everglades National Park

M.G. Winkler , P.R. Sanford , S. W. Kaplan, Center for Climatic Research, Institute for Environmental Studies, University of Wisconsin, Madison.

Paleoecological research provides knowledge of the prehistory of the Everglades which is crucial to

http://www.aoml.noaa.gov/flbay/sedi95.html (14 of 17)9/10/2007 2:32:43 PM Sedimentation & Paleoecology-1995 preservation and reconstruction efforts in southern Florida. The paleoenvironmental history of both the aquatic and hammock landscapes of the Everglades as interpreted from the biota preserved in sediment cores provides a chronology of hydrologic change, mid-Holocene sea level change, and upland vegetation change. Well-dated prehistoric sequences are still rare for the Everglades and, consequently, basic information about the past history of the Everglades is sparse. Our goal is to document in detail how anthropogenic activities in the last 100 years changed the Everglades environments and how climate change affected southern Florida before and during the Holocene. Knowledge of past changes in aquatic and upland plant communities in response to past climate change is also needed to predict the extent of future changes in the Everglades in light of possible carbon dioxide and methane-induced global warming.

Since 1993 we have been studying the paleoecology of sites in the Everglades National Park (ENP). We have 38 cores from 17 sites, mostly within ENP, although 4 sites are in Water Conservation Area 3 (WCA3), and 1 is at Lignum Vitae Key. Using radiocarbon dating and standard methods for paleoenvironmental research we have analyzed some of the sediments recovered for charcoal, pollen, diatoms, sponge spicules, cladocera, and Nymphaea and Cladium sclereids. The scarcity of pollen, diatoms, and other bioindicators in the sediments has slowed analyses and required modification of laboratory techniques. Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) and other chemical analyses of the more recent sediments and of fish scales from the cores have been used to reveal changes in nutrients and heavy metals. Charcoal analysis provides fire history of the peatlands. Because differences in stable carbon isotope signatures of C3 and C4 plants provide independent evidence of plant community change, mass spectrometric analyses of peats and charcoal from cores and plants near coring sites have been done.

Core sediment changes and 46 radiocarbon dates (by both AMS and standard bulk sediment techniques) provide a chronology for changes during the past 5000 years for ENP. Oldest dates, between 4900 and 5200 years before present (YBP) were obtained on cores from Rocky Glades, Pinelands trail, Castellow Hammock, L67C, and WCA3B. Freshwater marls were identified and dated for cross-correlation at most sites. Freshwater marl deposition results from lowered waterlevels. These deposits occur prior to 4000 YBP, between 2600 and 1900 YBP, and again after 1700 YBP. Overland flow may have been greatly diminished or confined to a few small channels during these periods. Relatively old dates on sediments near the upper part of some cores suggest that in the last centuries there were large water-level changes. These changes resulted in decomposition and loss of recent sediments during times of drought and the subsequent flushing of friable organic remains from sediments during times of high flow.

At Gator Lake pollen changes suggest a recent expansion of pinelands in the region. Pine also seems to have been abundant about 1500 YBP. Fluctuations between sawgrass and sedge pollen and aquatic macrophyte pollen, and pyrite framboid abundances indicate fluctuating water levels at Gator Lake. Diatom analysis indicates an inverse relationship between diatoms and sponges. Mercury analysis of fish scales found in the Gator Lake core revealed increased concentrations in the top sediments when compared to background (pre-European settlement) levels of mercury in both the fish scales and in the sediments surrounding the fish scales.

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Cores from 2 wet prairie/Eleocharis marsh sites in Northeast Shark Slough (NESS), A06 (a long hydroperiod site) and A23 (a short hydroperiod site), have been studied in detail. In addition to sediment description and radiocarbon dating, these cores have been analyzed for charcoal, Cladium sclereids, cladocera, sponge spicules, and for A23 only, pollen and Nymphaea sclereids. A23 has an older basal date (2840 YBP) than A06 (2100 YBP). The lower elevation of A23 with respect to bedrock allowed a rising water table, coupled to rising sea level, to affect A23 before it affected A06. Marl and peat deposits began to build up earlier at A23 than at A06. Dark organic marl at the base of A06, dated at 2100-1960 YBP, probably corresponds to an A23 mid-core marl dated at 1890 YBP. In both cores peat layers overlie these time-equivalent marl layers and presumably are also time-equivalent. A06 peat continues to the modern surface, but A23 peat is succeeded by an algal floc marl, then another peat (1380 YBP), and a final surface marly peat. An old date so near the surface suggests that deposits in the area of the A23 core have been truncated by decomposition when deposits were exposed by low water levels and by burning. Charcoal analysis of A23 deposits supports this hypothesis. The mean for charcoal as % organic in the A23 core is 67.08% (n=5),whereas for A06 the mean value for charcoal as % organic is 21.31% (n = 13) and in the most recent sample of the A06 deposits, 7-0 cm, charcoal was only about 13% of organic weight.

Cladium sclereid analysis indicates 3 periods of locally increased Cladium near A06, all since 1960 YBP, while at A23 only one such period (1890-1660 YBP) is evident. The single A23 peak may correspond to the lowermost A06 peak, any subsequent Cladium increases in A23 having been removed by decomposition and burning. Cladoceran remains are fewer and less taxonomically diverse at A23 (17 taxa) than at A06 (28 taxa). In both sites cladoceran remains are scarce at the base of the cores and increase gradually over time with final sharp increases in the surface core samples. Cladocera may be tracking periphyton production, which is in turn responding to water level and nutrient increases. The distribution pattern of cladoceran remains in the cores may indicate that significant periphyton production has occurred only recently. Sponge spicules are less numerous in A23 sediments than in A06 sediments, but in both cores they follow a distribution pattern similar to that of cladocera, being scarce in older deposits and increasing upcore. However there is no direct relationship between cladocera and sponges over time in either of the cores. If cladoceran pieces are tracking periphyton production, then the lack of a relationship between sponges and cladocera may reflect a competitive interaction between sponges and periphyton. There appears to be an inverse (A23) or lag (A06) relationship between sponge spicule densities and Cladium sclereid densities. Such relationships may reflect changing water levels if high numbers of Cladium sclereids indicate lower water levels and shorter hydroperiods and high numbers of sponge spicules indicate higher water levels and longer hydroperiods. Pollen analysis of A23 sediments is complicated by the fact that pine and cheno-am pollen overwhelmingly dominate most samples. The basal sample, however, is dominated by Isoetes microspores suggesting standing water during the initial phase of sediment deposition at A23. Nymphaea pollen is present in every sample, while Cyperaceae pollen is present in all but the basal one. Pollen of both taxa increases gradually through time. An early Cyperaceae peak is succeded by a peak in Typha, which is succeded by a peak in Nymphaea + Sagittaria + Utricularia + Cyperaceae. The fact that deposits are thinner and microscopic remains fewer in the older A23 core suggests that this area has always had lower water levels, shorter hydroperiods, and perhaps lower productivity than A06. The study of A06 and A23 shows that the rate of surface water flow is not uniform at sites within the Shark River Slough because slight topographic

http://www.aoml.noaa.gov/flbay/sedi95.html (16 of 17)9/10/2007 2:32:43 PM Sedimentation & Paleoecology-1995 differences can pool water or increase flow. Thus geomorphic changes can favor formation or degradation of peat or marl sediments and effect accompanying changes in local biota. These differences are evident in the formation and shaping of tree islands within the Shark River Slough, but they are also evident at more subtly different sites, as A06 and A23, by depositional differences in the past as well as today.

The modern hydrologic environment of the Everglades seems to be one of marl deposition. Recent hydrologic changes contrast with climate- and sea-level-induced changes over the past 5 millennia when deepwater peats formed, providing substrate for uplands, hammocks, and tree islands to enrich the landscape. The topographic highs in the landscape provide diverse habitat for both fauna and flora. The mosaic landscape of the Everglades could become less complex as long-term water-level changes may not favor production of peat today.

Work is continuing on this project. We are continuing detailed analyses of sediments from the sites with the longest records and hope to complete the study within the next year or two.

Last updated: 07/16/98 by: Monika Gurnée [email protected]

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New: >A Strategic Science Plan for Biscayne Bay - January 2002 >For more, click here to view the What's New Page...

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History...

Florida Bay is a triangularly shaped body of water about 2200 km2 in area. Over 85 percent of the Bay lies within Everglades National Park. Much of the remainder is in the Florida Keys National Marine Sanctuary. The Bay is bounded by the Florida Everglades on the north and the Florida Keys on the southeast and includes over 200 small islands or "keys", many of which are rimmed with mangroves and have interior irregularly flooded "flats" with calcareous algal mats. While Florida Bay is known as the principal inshore nursery for the offshore Tortugas pink shrimp, it also provides critical habitat for juvenile spiny lobsters, stone crabs, and many important finfish species. Moreover, the Bay supports numerous protected species including the bottle-nosed dolphin, the American crocodile, the West Indian manatee, and several species of sea turtles.

Shallow and often hypersaline, the Bay was until recently characterized by clear waters and lush seagrass meadows covering a mosaic of shallow water banks and numerous relatively deeper water basins. In western Florida Bay, seagrasses have been dying since the summer of 1987. A phenomenon such as this has not been observed previously in Florida Bay nor has a mass mortality of any tropical seagrass been reported in the scientific literature. In some areas vegetative cover has been partially re-established by either the original species or another species, but in other areas recolonization has been slow and large areas of the bottom are still devoid of vegetation.

There are other indications that the environmental health of Florida Bay has deteriorated. Fishing success has declined for many of the commercial and recreational species that depend upon the Bay as a juvenile nursery habitat, suggesting a decline in recruitment. Atypical algal blooms have been reported in the last few years across much of western Florida Bay and have extended into the Florida Keys. These blooms are thought to have attributed to the Loggerhead sponge die-off. This is significant because these sponges are the habitat for juvenile lobster. Most recently, mangroves within the Bay are reported to be in decline. While the causes of the various problems and the relationships between them are not well understood, there is no question that, like the sawgrass habitat of the

http://www.aoml.noaa.gov/flbay/program_overview.html (1 of 3)9/10/2007 2:32:46 PM Florida Bay & Adjacent Marine Systems Everglades, the coastal marine ecosystem of Florida Bay is in jeopardy.

More freshwater alone will not return Florida Bay to its pristine condition. The timing, location, and quality of freshwater released to Florida Bay must also be considered. Water quality is particularly important, and measures to address pollution specific to the Everglades may not be adequate to protect Florida Bay. Increasing freshwater flow to the Bay, all else being equal, could increase nutrient loading which might induce more frequent and more extensive phytoplankton blooms. These could, in turn, result in further losses of bottom vegetation in the Bay from light limitation, and nutrient loads in Bay waters that exit between the Keys could be injurious to the coral reefs of the Florida Keys Marine Sanctuary. Lastly, increasing water flow could also increase trace contaminant loading depending on sources and flow pathways.

At present, there is insufficient scientific knowledge to predict with confidence the consequences of anticipated alterations in freshwater input to Florida Bay. Although increased flow can certainly reduce the frequency and severity of hypersalinity, fine-tuning of water flow, reduction in plant nutrient concentrations in in-flowing water, and other corrective measures may also be necessary to restore the health and productivity of the Bay.

Since no one can turn back the clock and South Florida's rapid development will almost certainly continue, a series of compromises and tradeoffs will have to be made in restoring and maintaining a healthy South Florida coastal ecosystem including Florida Bay. It is essential that decisions be made based on reliable scientific information. To generate the requisite information a group of federal and state agencies are collaborating in an interagency Florida Bay Science Program that conducts closely complementary research, monitoring, and modeling projects which together will answer the most critical scientific questions about the Bay ecosystem. This program is guided by a Program Management Committee (PMC) that has recently expanded to assure coordination and collaboration with developing programs at Biscayne Bay, Rookery Bay, the Florida Keys National Marine Sanctuary, and the Dry Tortugas in so far as they are germane to South Florida ecosystem restoration.

The Bigger Picture...

The Florida Bay and Adjacent Marine Systems Science Program is a scientific component of the much larger South Florida Ecosystem Restoration initiative headed by a Task Force consisting of state and federal agency heads and representatives from other stakeholder groups. Reporting to the Task Force are a group of regional managers (Working Group) of those agencies responsible for managing the environmental resources in South Florida and carrying out the restoration activities. This Working Group has established among other

http://www.aoml.noaa.gov/flbay/program_overview.html (2 of 3)9/10/2007 2:32:46 PM Florida Bay & Adjacent Marine Systems committees a Science Coordination Team (SCT) responsible for defining and developing plans to provide the scientific and information needs of the Working Group. In doing so, South Florida has been divided into a series of subregions, one of which includes Florida Bay. Results of Florida Bay’s science program are communicated to the Working Group and its subgroups through the annual Florida Bay Science Conference, joint membership of some PMC members on the Science Coordination Team, and by direct briefing of agency managers.

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2002 Calendar

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May June July August

September October November December

http://www.aoml.noaa.gov/flbay/calendar_main.html9/10/2007 2:32:49 PM

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Universe of knowledge Central questions about Biscayne Bay Yr. 2002 priority items

Figure 1. Relationship of central questions and highest priority items.

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Figure 2. The watershed of Biscayne Bay contains extensive urban (gray) and agricultural (yellow) areas transected by water management canals. Wetlands border the southern portion.

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(OYIG_TK (G_ 9IOKTIK 6RGT Page  63) SPECIFIC, SHORT TERM GENERAL INFORMATION GOAL OBJECTIVES NEEDS NEEDS

1.a. Little surface water salinity data available nearshore. Collect more data.

2.a. Distribution and abundance of fish and shrimp unknown along coast. Collect data.

Need to know: Existing character. 1.c.i) Uncertainty about actual canal discharge volumes. Improve data accuracy.

1.c.ii) Relationship of rainfall to surface water flow poorly understood. Recreate a more Determine relationship. mesohaline habitat along southwestern coast. 1.d. Influence of groundwater on ecology poorly understood. Determine significance.

1.b. Uncertain how hydrodynamics and salinity patterns respond. Develop numerical, predictive Restore estuarine Need to know: How models. Could include statistical systems operate/ and mechanistic models. character. respond to changes.

1.e. Mechanistic models will require accurate bathymetry/wetland topography. Collect data.

1.f. Sea levels are rising. Uncertain how this will affect restoration. Reconnect wetlands/ Improve forecasts. oligohaline habitats.

2.c. Relationships of substrate, salinity and SAV not well understood. Describe relationship along S.W. coast.

Need to know: 1.g. Predevelopment salinity patterns Appropriate poorly understood. Extend paleo, benchmark or goal isotopic and other methods to hindcast Bay character. to achieve.

1.h. Inflows along southwest coast changed. Define required inflows to maintain mesohaline conditions.

2.b. Importance of key factors influencing diatom, shrimp & bivalve production not well understood. ,QIRUPDWLRQ Establish relationships as indicators.

Figure 3. Research and monitoring needs related to the management goal to restore the estuarine character of Biscayne Bay. Information flows from data collection tasks to answer critical questions about how to achieve strategic objectives, and ensure effectiveness.

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3.d. Comparative information is essential to understand patterns. Continue comprehensive water quality, bioeffects monitoring, and indicator research.

3.e. Influence of groundwater quality on ecology poorly Need to know: understood. Determine Existing character. significance.

3.f. Concentrations and safety of toxicants in tissues are not well established. Collect baseline data.

Control watershed loading. 3.g. Toxicant load in wetland soils unknown. Collect baseline data.

3.h. Nutrient flux from atmosphere and between sediments and water not well Eliminate pollutant Need to know: How understood. Collect baseline systems operate/ data. impacts. respond to changes.

3.i. Fish exhibit high rate of physical abnormalities. Determine causes.

3. b,c. Uncertain how water Ensure human health. quality patterns respond. Develop numerical, predictive models. Could include statistical and mechanistic models.

3.a. Relationships between water quality and ecosystem health is not well understood. Need to know: Develop an approach for Appropriate numerical water quality targets. benchmark or goal to achieve.

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Figure 4. Research and monitoring needs related to the management goal to eliminate pollution impacts in Biscayne Bay. Information flows from data collection tasks to answer critical questions about how to achieve strategic objectives, and ensure effectiveness.

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2.d. Utilization of freshwater habitats poorly understood. Collect baseline data.

2.e. Utilization/importance of fish of North Bay habitats not established. Collect baseline Need to know: data. Existing character.

2.f. Utilization/importance of mangrove habitat to juveniles not established. Collect baseline data.

Ensure healthy fish 3.f. Concentrations and safety of and shrimp toxicants in tissues are not well populations. established. Collect baseline data.

4.b. Population structure of key species not well defined. Collect data and describe structure. Restore sustainable Need to know: How systems operate/ fisheries. respond to changes.

4.a. Uncertain how fishing pressure affects populations. Collect comprehensive data.

4.a.ii) Sustainability of pink Protect and restore shrimp fishery uncertain. Assess fish habitats. impact of bycatch, and analyze fishing statistics.

4.d. Fishing methods have an unknown impact on benthic communities. Assess impacts. Need to know: Appropriate benchmark or goal to achieve. 4.e. Relationship of fishery production to variables not well understood. Develop models.

4.c. Habitat requirements for small fish sizes mostly unknown. Determine requirements. ,QIRUPDWLRQ

Figure 5. Research and monitoring needs related to the management goal to restore sustainable fisheries in Biscayne Bay. Information flows from data collection tasks to answer critical questions about how to achieve strategic objectives, and ensure effectiveness.

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